Sci . El ect r oni oni cs FA FAQ: Repai r : TV Repai r Not es on TV Repai epai r and and Di agno agnosi si s I NDEX V2. 20 ( 3/ 26/ 96) Tabl e of Cont ent s Chapt hapt er 1) About bout t he Aut hor hor & Copyr opyr i ght ght Chapt er 2) I nt r oduct i on 2. 1) Tel evi si on at t he cr ossr oads 2. 2) Tel evi si on r ecei cei ver ver f undament al s 2. 3) TV r epai r 2. 4) Repai r or r epl ace Chapt hapt er 3) 3) TV Recei ecei ver ver s 101 101 3. 1) Subsyst ems of a t el evi si on set set 3. 2) For For mor e i nf or mat i on on TV t echn echnol ogy ogy Chapt hapt er 4) CRT Basi cs 4. 1) Col or CR CRTs, Shad Shadow owmasks, Magne agnett i c Fi el ds, and and Degau egauss ss 4. 2) Why i s t he Shad Shadow owmask or or Aper per t ur e Gr i l l made ade of a magne agnett i c mat er i al ? 4. 3) Tubes f or al al l Nat i ons 4. 4) Degau egauss ss i ng ( dem demagne agnett i zi ng) ng) a CRT 4. 5) Why ar e i ndi ndi r ect l y heat eat ed cat hodes odes used i n CRT 4. 6) Why do TVs TVs over over scan? sc an? 4. 7) Scr at che ches i n CRT f ace Chapt hapt er 5) TV Pl acement ent and and Pr even eventt i ve Mai nt enan enance ce 5. 1) Gener ener al TV pl acem acement ent consi consi der at i ons ons 5. 2) Pr even eventt i ve mai nt enan enance ce Chapt apt er 6) TV Tr oubl oubl eshoo eshoott i ng 6. 1) Saf et y 6. 2) Saf et y Gui del i nes 6. 3) Tr oubl esho shoot i ng t i ps 6. 4) Test Test eq equi pment ent 6. 5) I ncr edi edi bl y Hand andy wi dget s 6. 6) Saf e di schargi schargi ng of capaci capaci t or s i n TVs TVs and and vi deo moni oni t ors 6. 7) The ser ser i es l i ght bu bul b t r i ck 6. 8) Get t i ng i nsi de a TV 6. 9) Dust i ng out t he i nsi de of a TV Chapt hapt er 7) 7) TV Adj ust ment ent s 7. 1) User pi ct ur e adj adj ust ment 7. 2) Focu Focus s adj adj ust ment ent 7. 3) Adj ust ment of t he i nt er nal SCREEN and and col or cont cont r ol s 7. 4) Col or Bal ance ance 7. 5) Hor i zon zont al posi t i on, si ze, ze, and l i near i t y adj ust ment 7. 6) Ver t i cal cal posi t i on, si ze, ze, and l i near i t y adj ust ment 7. 7) Pi ncush cushii on adj adj ust ment ent s 7. 8) Geom eomet r y adj adj ust ment ent 7. 9) Why i s t he conver conver gence gence on my set bad near near t he edge edges s 7. 10) CRT pur i t y and and conve converr gence ence pr obl obl em 7. 11) CRT pur i t y adj adj ust ment ent 7. 12) 12) CRT conver conver gence gence adj ust ment ent 7. 13) Ti l t ed pi ctur ctur e Chapt hapt er 8) Low Vol t age age Power Supp Suppll y Pr obl ems 8. 1) Low vol t age age pow power suppl suppl y f unda undam ment ent al s 8. 2) Power but but t on on set set i s f l akey key 8. 3) TV bl ows f use 8. 4) I nt er nal f use bl ew dur i ng l i ght eni ng st or m ( or el ephant hi t power pol pol e) 8. 5) Fuse Fuse r epl aced aced but TV cl i cks wi t h power - on but no ot her act i on 8. 6) Power - on t i c kk- t i c kk- t i c k or c l i c kk- c l i c kk- c l i c k but no no ot her ac ac t i on
8. 7) No pi ct ur e or r ast er and and no soun sound 8. 8) Reduced ced wi dt h pi ct ur e and and/ or hu hum bars i n pi ct ur e and and/ or hu hum i n soun sound 8. 9) TV power cycl i ng on and and of f 8. 10) Dead TV wi t h per i odi odi c t weet - t weet - t weet or f l ub- f l ub- f l ub 8. 11) 11) Shor Shor t ed Componen ponentt s 8. 12) St ar t up pr obl ems - no not hi ng happens, cl i ck, ck, or t i ckck- t i ckck- t i ck sou sound 8. 13) TV t ur ns of of f af t er warm warmi ng up 8. 14) 14) TV doesn doesn'' t power up i mmedi edi at el y 8. 15) 15) Ol d TV r equi equi r es war mup per per i od 8. 16) Rel ays ays i n t he Power C Cii r cui cui t r y of TVs 8. 17) Fl amepr oof Resi st ors Chapt apt er 9) Def l ect i on Pr obl obl ems 9. 1) Def l ect ect i on f undament al s 9. 2) Why ar e near l y al l hor i zon zont al dr i ver ver s ci ci r cui cui t s tr ansf or mer coup coupl ed? 9. 3) Pi ct ur e sque squeezed i n t hen di ed 9. 4) Hor i zont zont al def def l ect i on shu shut t i ng down 9. 5) Hor i z on ont al l oc k l os t 9. 6) Ver t i cal cal squ squashe shed 9. 7) Par t of of pi pi c t ur ur e c ut ut of of f 9. 8) Si ngl e Ver t i cal cal Li ne 9. 9) Si ngl e Hor i zon zont al Li ne 9. 10) Loss Loss of of Hor i zont zont al Sync ync ( al so appl i es to ver ver t i cal cal ) af t er War mup 9. 11) I nt er mi t t ent j umpi ng or j i t t er i ng of pi ct ur e or ot her r andom behavi or 9. 12) Hor i zon zont al out out put t r ansi st or s kee keep bl owi ng 9. 13) Ver t i cal cal f ol dover 9. 14) 14) Squa Squashe shed d pi ct ur e on l at e model odel GE, RCA, or Pr oScan oScan TV 9. 15) Pi ncush cushii oni oni ng Probl Probl ems 9. 16) Test i ng of f l yba yback ( LOPT) PT) t r ansf ormer s Chapt hapt er 10) 10) Hi gh Vol t age age Pow Power Supp Suppll y Pr obl obl ems 10. 10. 1) HV power suppl suppl y f unda undam ment ent al s 10. 2) What i s a t r i pl er ? 10. 3) Hi gh vol vol t age shu shut down due t o X- r ay pr otect i on ci r cui cui t s 10. 10. 4) Low or no no hi gh vol vol t age age 10. 5) Excessi xcessi ve hi gh vol vol t age age 10. 6) Ar ci ng, spar spar ki ng, or cor cor ona ona f r om CRT HV anod anode e ( r ed wi r e/ suct suct i on cup cup) 10. 10. 7) Ar ci ng at CR CRT spar spar kgap kgaps s 10. 8) Ar c i ng f r om f l ybac k or vi vi c i ni t y 10. 10. 9) Ozone smel l and/ and/ or smoke f r om TV 10. 10) Shoul oul d I be worr i ed abou aboutt X- r ay exposu xposurr e whi l e servi ci ng a TV or moni oni t or? 10. 10. 11) Fl yback yback shot shot by 4 year year ol d Chapt apt er 11 11) Rast er , Col or , and and Vi deo deo Pr obl obl ems 11. 1) No col col or - bl ack and and whi t e pi ct ur e 11. 2) Psych sycho odel i c col col or 11. 3) TV and and Moni oni t or Manu anuf act act ur i ng Qual i t y and and Col d Sol der J oi nt s 11. 4) I nt er mi t t ent or or Mi ssi ng Col or s 11. 5) Red, gr een, or bl ue f ul l on - f og over pi ct ur e 11. 6) Pr ovi di ng i sol sol at i on f or a CRT H- K sho shor t 11. 11. 7) Rescui ng a shor t ed CRT 11. 11. 8) Br i ght ght eni eni ng an ol d CRT 11. 9) Bl eedi ng hi ghl i ght s 11. 10) Tr ai l i ng l i nes on one or more col col or s 11. 11) Pi ct ur e f ades i n and out out 11. 12) Occasi ccasi onal br i ght ness f l ashe shes 11. 13) Excessi xcessi ve br i ght ness an and/ or wash washe ed out out pi ct ur e 11. 14) Bad f ocus cus ( f uzzy pi ct ur e) 11. 11. 15) Focus Focus dr i f t wi t h war mup or age age 11. 11. 16) 16) Bad f ocus ocus and and adj adj ust ment ent change changes s br br i ght ght ness ness 11. 11. 17) Bl ank ank pi ct ur e, good ood chan channel t uni ng and and soun sound
8. 7) No pi ct ur e or r ast er and and no soun sound 8. 8) Reduced ced wi dt h pi ct ur e and and/ or hu hum bars i n pi ct ur e and and/ or hu hum i n soun sound 8. 9) TV power cycl i ng on and and of f 8. 10) Dead TV wi t h per i odi odi c t weet - t weet - t weet or f l ub- f l ub- f l ub 8. 11) 11) Shor Shor t ed Componen ponentt s 8. 12) St ar t up pr obl ems - no not hi ng happens, cl i ck, ck, or t i ckck- t i ckck- t i ck sou sound 8. 13) TV t ur ns of of f af t er warm warmi ng up 8. 14) 14) TV doesn doesn'' t power up i mmedi edi at el y 8. 15) 15) Ol d TV r equi equi r es war mup per per i od 8. 16) Rel ays ays i n t he Power C Cii r cui cui t r y of TVs 8. 17) Fl amepr oof Resi st ors Chapt apt er 9) Def l ect i on Pr obl obl ems 9. 1) Def l ect ect i on f undament al s 9. 2) Why ar e near l y al l hor i zon zont al dr i ver ver s ci ci r cui cui t s tr ansf or mer coup coupl ed? 9. 3) Pi ct ur e sque squeezed i n t hen di ed 9. 4) Hor i zont zont al def def l ect i on shu shut t i ng down 9. 5) Hor i z on ont al l oc k l os t 9. 6) Ver t i cal cal squ squashe shed 9. 7) Par t of of pi pi c t ur ur e c ut ut of of f 9. 8) Si ngl e Ver t i cal cal Li ne 9. 9) Si ngl e Hor i zon zont al Li ne 9. 10) Loss Loss of of Hor i zont zont al Sync ync ( al so appl i es to ver ver t i cal cal ) af t er War mup 9. 11) I nt er mi t t ent j umpi ng or j i t t er i ng of pi ct ur e or ot her r andom behavi or 9. 12) Hor i zon zont al out out put t r ansi st or s kee keep bl owi ng 9. 13) Ver t i cal cal f ol dover 9. 14) 14) Squa Squashe shed d pi ct ur e on l at e model odel GE, RCA, or Pr oScan oScan TV 9. 15) Pi ncush cushii oni oni ng Probl Probl ems 9. 16) Test i ng of f l yba yback ( LOPT) PT) t r ansf ormer s Chapt hapt er 10) 10) Hi gh Vol t age age Pow Power Supp Suppll y Pr obl obl ems 10. 10. 1) HV power suppl suppl y f unda undam ment ent al s 10. 2) What i s a t r i pl er ? 10. 3) Hi gh vol vol t age shu shut down due t o X- r ay pr otect i on ci r cui cui t s 10. 10. 4) Low or no no hi gh vol vol t age age 10. 5) Excessi xcessi ve hi gh vol vol t age age 10. 6) Ar ci ng, spar spar ki ng, or cor cor ona ona f r om CRT HV anod anode e ( r ed wi r e/ suct suct i on cup cup) 10. 10. 7) Ar ci ng at CR CRT spar spar kgap kgaps s 10. 8) Ar c i ng f r om f l ybac k or vi vi c i ni t y 10. 10. 9) Ozone smel l and/ and/ or smoke f r om TV 10. 10) Shoul oul d I be worr i ed abou aboutt X- r ay exposu xposurr e whi l e servi ci ng a TV or moni oni t or? 10. 10. 11) Fl yback yback shot shot by 4 year year ol d Chapt apt er 11 11) Rast er , Col or , and and Vi deo deo Pr obl obl ems 11. 1) No col col or - bl ack and and whi t e pi ct ur e 11. 2) Psych sycho odel i c col col or 11. 3) TV and and Moni oni t or Manu anuf act act ur i ng Qual i t y and and Col d Sol der J oi nt s 11. 4) I nt er mi t t ent or or Mi ssi ng Col or s 11. 5) Red, gr een, or bl ue f ul l on - f og over pi ct ur e 11. 6) Pr ovi di ng i sol sol at i on f or a CRT H- K sho shor t 11. 11. 7) Rescui ng a shor t ed CRT 11. 11. 8) Br i ght ght eni eni ng an ol d CRT 11. 9) Bl eedi ng hi ghl i ght s 11. 10) Tr ai l i ng l i nes on one or more col col or s 11. 11) Pi ct ur e f ades i n and out out 11. 12) Occasi ccasi onal br i ght ness f l ashe shes 11. 13) Excessi xcessi ve br i ght ness an and/ or wash washe ed out out pi ct ur e 11. 14) Bad f ocus cus ( f uzzy pi ct ur e) 11. 11. 15) Focus Focus dr i f t wi t h war mup or age age 11. 11. 16) 16) Bad f ocus ocus and and adj adj ust ment ent change changes s br br i ght ght ness ness 11. 11. 17) Bl ank ank pi ct ur e, good ood chan channel t uni ng and and soun sound
11. 18) Pur Pur pl e bl ob - or wors e 11. 19) Col or TV onl y di spl spl ays one col col or 11. 20) Di sapp sappeari ng Red ( or ot her col or ) Chapt hapt er 12) Tuner Tuner and AGC Pr obl ems 12. 1) No r ecep cept i on f r om ant ant enna or cab cabll e 12. 2) Pi ct ur e i s over ver l oade aded, washe shed out , or noi noi sy 12. 12. 3) I nt er f er ence ence when usi ng VCR RF conn connect i on 12. 4) Mi ssi ng or noi noi sy chan chann nel or bl bl ock ock of chan channel s 12. 12. 5) Loss of of Chann hannel el af t er War mup 12. 6) Chann annel t uni ng dr i f t s as as set set warms up up 12. 7) Noi se i n pi ct ur e and and soun sound due t o br i ght scene scene Chapt hapt er 13) 13) Audi udi o Pr obl obl ems 13. 1) Pi ct ur e f i ne, no audi o 13. 2) Weak or di di st or t ed aud audi o 13. 13. 3) Buzzi ng TV 13. 13. 4) Hi gh pi t ched ched whi ne or s queal eal f r om TV wi t h no ot her s ympt oms Chapt apt er 14 14) Mi scel l aneo aneous us Pr obl obl ems 14. 1) Gener al err at i c behavi or 14. 2) J i t t er i ng or f l i cker cker i ng due t o pr obl ems wi t h AC power 14. 14. 3) My TV has has t he shakes 14. 14. 4) TV was r ai ned ned on 14. 14. 5) TV was dr oppe opped d 14. 14. 6) Set up menu enus wi l l not not go away or hi er ogl ogl yphi yphi cs on scr een een 14. 14. 7) Set up Adj ust ment ent s Lost 14. 8) TV doesn oesn'' t wor wor k af t er bei bei ng i n st orage orage 14. 9) Ol der TVs TVs wi t h mul t i pl e i nt er mi t t ent pr obl ems 14. 14. 10) TV has bur bur ni ng smel l 14. 11) Revi val val of dead or t i r ed r emot e con cont r ol uni t s 14. 14. 12) 12) Loudspeake Loudspeakerr s and and TVs TVs 14. 13) Shoul d I r epl ace al l t he el ectr ol yt i c ca capaci t or s i f I f i nd a bad one? 14. 14) Phant ant om spo spot or bl ob on CRT af t er set i s shu shut of f 14. 14. 15) 15) Di sposi ng of dead dead TVs TVs ( CRTs and and char char ged ged HV capaci capaci t or s) Chapt er 15 15) I t ems of I nt er est 15. 1) An i nf or mal hi st or y of X- r ay pr ot ect i on 15. 15. 2) Memor y chi ps i n TVs TVs 15. 15. 3) Ton Tony' s not not es on on set t i ng conve converr gence ence on del t a gun CRTs 15. 15. 4) Saga aga and and gener ener al set up f or l ar ge CRT TVs TVs 15. 15. 5) About out I nst ant ant On On TVs TVs 15. 15. 6) Can I add add an S- Vi deo deo i nput nput t o my TV TV or VCR? 15. 15. 7) How do I add add A/ V i nput s t o a TV whi ch does oes not not have ave t hem bui l t i n? 15. 8) Tur ni ng a TV ( or moni t or) i nt o an osci l l oscop scope? 15. 9) Di spl spl ayi ng a vi deo si gnal as a pi ct ur e on an osci l l osco oscope 15. 10) Use of s ur ge sup suppr essors an and l i ne f i l t er s 15. 11) GFC FCII t r i ppi ng wi t h moni oni t or ( or ot her hi gh t ech equi pment ) 15. 12) Mul t i syst em TVs 15. 13) Coul oul d a TV be modi odi f i ed f or 3D ( st er eo) di spl spl ay? ay? 15. 15. 14) 14) Di spl ayi ng TV on a comput put er moni oni t or 15. 15. 15) 15) Di spl ayi ng comput put er vi deo deo on a TV 15. 16) What i s Ke Kel l f act or wi wi t h r espe spect t o i nt er l aced ced di spl spl ays? 15. 17) Homemade ade V- chi chi p ( or at l east vi ewi ng l i mi t er 15. 15. 18) I nt er est i ng TV Swi t ch Mode ode Pow Power Sup Suppl y 15. 19) I R det ector ci r cui cui t Chapt er 16 16) I nt er nati onal Co Col or Te Tel evi si on St andar ds 16. 16. 1) Som Some quest quest i ons and and answ answer er s abou aboutt TV st andar andar ds 16. 2) Pol i t i cal cal l y Cor r ect TV St andar ds 16. 3) Var i at i ons on a ' st andard' - t he PAL syst em 16. 4) Col or t el evi si on st andards wor l dwi de 16. 5) Cabl e chan chann nel al l oca ocat i on
16. 6) Not es on cabl e and br oadcast f r equenci es 16. 7) Why i s t he NTSC col or subcar r i er such a wei r d f r equency? 16. 8) What i s t he maxi mal al l owed devi at i on of t he hor i zont al f r equency? 16. 9) I nf or mal compar i son of TV st andar ds Chapt er 17) Repai r I nf or mat i on and Par t s Sour ces 17. 1) Advanced TV t r oubl eshoot i ng 17. 2) Ser vi ce manual s f or r eal l y ol d TVs 17. 3) Par t s i nf or mat i on 17. 4) I nf ormat i on sour ces on t he I nt er net 17. 5) Suggest ed r ef er ences 17. 6) I nt erchangeabi l i t y of component s 17. 7) Repai r part s sour ces: Chapt er 1)
About t he Aut hor & Copyr i ght
Aut hor : Samuel M. Gol dwasser E- Mai l : sam@st davi ds. pi cker . com Copyr i ght ( c) 1994, 1995, 1996 Al l Ri ght s Reser ved Repr oduct i on of t hi s document i n whol e or i n par t i s per mi t t ed i f bot h of t he f ol l owi ng condi t i ons ar e sat i sf i ed: Thi s not i ce i s i ncl uded i n i t s ent i r et y at t he begi nni ng. Ther e i s no char ge except t o cover t he cos t s of copyi ng. Chapt er 2) 2. 1)
I nt r oduct i on
Tel evi si on at t he cr ossr oads
Tel evi si on i n subst ant i al l y i t s pr esent f or m has been wi t h us f or near l y 50 years. I t i s a t r i but e t o t he Nat i onal Tel evi si on St andar ds Commi t t ee ( NTSC) t hat t he col or t el evi si on st andar ds agr eed upon i n t he ear l y 1950s have per f or med r emar kabl y wel l maki ng qui t e ef f i ci ent use of val uabl e r adi o spect r um space and t he psychovi sual char act er i st i cs of t he human eye- br ai n syst em. However , HDTV ( Hi gh Def i ni t i on TV) wi l l suppl ant and ul t i mat el y r epl ace t he cur r ent st andar ds. We wi l l al l come t o expect i t s super i or r esol ut i on, f r eedom f r om noi se and ghost i ng, and CD sound. Yet , t he per cei ved qual i t y of TV br oadcast s and cabl e wi l l never l i kel y be the maj or i ssue wi t h most consumer s. Cont ent wi l l cont i nue t o be t he bi ggest pr obl em. I t i s l i kel y t hat i n r oughl y 15 year s, HDTV - di gi t al l y pr ocessed and t r ansmi t t ed as 1s and 0s - wi l l compl et el y r epl ace t he cur r ent syst em. Accept ance i n t he mar ket pl ace i s by no means assur ed but wi t h t he mer gi ng of TV and comput er s - wi t h t he I nt ernet as a dr i vi ng f orce - i t woul d seem t hat t he days of t he st and- al one anal og TV set ar e number ed. 2. 2)
Tel evi si on r ecei ver f undament al s
The basi c col or t el evi si on r ecei ver must per f or m t he same f unct i ons t oday as 40 years ago. ( Si nce B/ W i s a subset of t he col or st andar d, most r ef er ences i n t hi s document wi l l be f or col or except as not ed) . A st udi o vi deo moni t or i ncl udes al l of t he f unct i ons of a t el evi si on r ecei ver except t he t uner and I F ( whi ch r arel y f ai l except f or bad connect i ons or per haps l i ght eni ng st r i kes t o t he ant enna or cabl e connect i on) . Theref or e most of t he repai r i nf or mat i on i n t hi s document i s appl i cabl e to bot h TVs and st udi o moni t ors . Moder n comput er moni t or s share many si mi l ari t i es wi t h TVs but t he mul t i sync and hi gh sc an r at e def l ect i on ci r cui t r y and mor e
sophi st i cat ed power suppl i es compl i cat es t hei r ser vi ci ng. As of t hi s wr i t i ng, al l but t he smal l est TVs are based on t he Cat hode Ray Tube ( CRT) as t he di spl ay devi ce. Ti ny pocket set s, camcor der vi ewf i nder s, and t he l i ke have st ar t ed usi ng LCD ( Li qui d Cr ystal Di spl ay) panel s but t hese ar e st i l l i nf er i or t o the CRT f or r eal t i me vi deo. Ther e has al ways been t al k of ' t he pi ct ur e on t he wal l ' di spl ay. Whi l e we ar e cl oser t han ever t o thi s possi bi l i t y, I bel i eve that mass pr oduct i on of an af f or dabl e wal l mur al TV scr een i s st i l l decades away. The r eason i s si mpl e economi cs - i t i s r eal l y har d t o beat t he si mpl i ci t y of t he shadowmask CRT. For exampl e, a decent qual i t y act i ve mat r i x col or LCD panel may add $1000 t o t he cost of a not ebook comput er compar ed t o $200 f or a VGA moni t or . Mor e of t hese panel s go i n t he dumpst er t han make i t t o pr oduct do t o manuf act ur i ng i mperf ect i ons. Pr oj ect i on - l ar ge scr een - TVs may, on t he ot her hand, be abl e t o t ake advant age of a novel devel opment i n i nt egr at ed mi cr omachi ni ng - t he Texas I nst r ument s I nc. Di gi t al Mi cr omi r r or Devi ce ( DMD) . Thi s i s basi cal l y an i nt egr at ed ci r cui t wi t h a ti l t abl e mi cromi r r or f or each pi xel f abr i cat ed on t op of a st at i c memory - RAM - cel l . Thi s t echnol ogy woul d per mi t near l y any si ze pr oj ect i on di spl ay t o be pr oduced and woul d t her ef or e be appl i cabl e t o HDTV. Si nce i t i s a r ef l ect i ve devi ce, t he l i ght sour ce can be as br i ght as needed. However , t hi s i s sti l l not a commer ci al pr oduct but st ay t uned. 2. 3)
TV r epai r
Unl i ke VCRs or CD pl ayer s wher e any di saster s ar e l i kel y t o onl y af f ect your pocket book, TVs can be danger ous. Read, under st and, and f ol l ow t he set of saf et y gui del i nes pr ovi ded l at er i n t hi s sect i on whenever wor ki ng on TVs, moni t ors , or ot her si mi l ar hi gh vol t age equi pment . I f you do go i nsi de, beware: l i ne vol t age (on l ar ge caps) and hi gh vol t age ( on CRT) f or l ong af t er t he pl ug i s pul l ed. Ther e i s t he added danger of CRT i mpl osi on f or carel essl y dr opped t ool s and of t en sharp sheet met al shi el ds whi ch can i nj ur e i f you shoul d have a r ef l ex r eact i on upon t ouchi ng somet hi ng you shoul d not t ouch. I n i nsi de of a TV or moni t or i s no pl ace f or t he car el ess or nai ve. Havi ng sai d t hat , a basi c knowl edge of how a TV set wor ks and what can go wr ong can be of gr eat val ue even i f you do not at t empt t he r epai r your sel f . I t wi l l enabl e you t o i nt el l i gent l y deal wi t h t he ser vi ce t echni ci an. You wi l l be mor e l i kel y to be abl e t o r ecogni ze i f you ar e bei ng t aken f or a r i de by a di shonest or j ust pl ai n i ncompet ent r epai r cent er . For exampl e, a f aul t y pi ct ur e t ube CANNOT be t he cause of a col or t el evi si on onl y di spl ayi ng shows i n bl ack- and- whi t e. The maj or i t y of consumer s pr obabl y do not know even t hi s si mpl e f act . Such a pr obl em i s usual l y due t o a bad capaci t or or ot her 10 cent par t . Thi s document wi l l pr ovi de you wi t h t he knowl edge t o deal wi t h a l ar ge per cent age of t he pr obl ems you ar e l i kel y t o encount er wi t h your TVs. I t wi l l enabl e you t o di agnose pr obl ems and i n many cases, cor r ect t hem as wel l . Wi t h mi nor except i ons, speci f i c manuf act ur er s and model s wi l l not be cover ed as t her e ar e so many var i at i ons t hat such a t r eat ment woul d r equi r e a huge and ver y det ai l ed t ext . Rat her , t he most common pr obl ems wi l l be addr essed and enough basi c pr i nci pl es of oper at i on wi l l be pr ovi ded t o enabl e you t o nar r ow t he pr obl em down and l i kel y det er mi ne a cour se of
act i on f or r epai r . I n many cases, you wi l l be abl e t o do what i s r equi r ed f or a f r act i on of t he cost t hat woul d be char ged by a r epai r cent er . Shoul d you st i l l not be abl e t o f i nd a sol ut i on, you wi l l have l ear ned a gr eat deal and be abl e t o ask appr opr i at e quest i ons and suppl y r el evant i nf ormat i on i f you dec i de t o pos t t o s ci . el ec t r oni c s. r epai r . I t wi l l al s o be eas i er t o do f ur t her r esear ch usi ng a repai r t ext such as t he ones l i st ed at t he end of t hi s document . I n any case, you wi l l have t he sat i sf act i on of knowi ng you di d as much as you coul d bef or e t aki ng i t i n f or pr of essi onal r epai r . Wi t h your new- f ound knowl edge, you wi l l have t he upper hand and wi l l not easi l y be snowed by a di shonest or i ncompet ent t echni ci an. 2. 4)
Repai r or r epl ace
I f you need t o send or t ake t he TV t o a ser vi ce cent er , t he r epai r coul d easi l y exceed hal f t he cost of a new TV. Ser vi ce cent er s may charge up t o $50 or more f or pr ovi di ng an i ni t i al est i mat e of r epai r cost s but t hi s wi l l usual l y be credi t ed t owar d t he t ot al cost of t he r epai r ( of cour se, t hey may j ust j ack t hi s up t o compensat e f or t hei r bench t i me) . TV pr i ces have been dr oppi ng al most as f ast as PC pr i ces. Ther ef or e, payi ng such pr i ces f or r epai r j ust may not make sense. Except f or pi ct ur e t ube pr obl ems, most TV f aul t s can be cor r ect ed wi t hout expensi ve par t s, however . Keepi ng a 5 year ol d TV al i ve may be wel l wor t hwhi l e as basi c TV per f or mance and i mpor t ant f eat ur es have not changed i n a l ong t i me. I f you can do t he repai r s your sel f , t he equat i on changes dr amat i cal l y as your par t s cost s wi l l be 1/ 2 t o 1/ 4 of what a pr of essi onal wi l l char ge and of cour se your t i me i s f r ee. The educat i onal aspect s may al so be appeal i ng. You wi l l l ear n a l ot i n t he pr ocess. Thus, i t may make sense t o r epai r t hat ol d cl unker f or your game r oom or beach house. ( I woul d suggest t he ki d' s r oom but most TV wat chi ng j ust r ot s t he br ai n anyhow so a br oken TV may be mor e wor t hwhi l e educat i onal l y t han one t hat wor ks. ) Chapt er 3) 3. 1)
TV Recei ver s 101
Subsyst ems of a t el evi si on set
A TV set i ncl udes t he f ol l owi ng f unct i onal bl ocks: Low vol t age power s uppl y ( some may al so be par t of ( 2) ) . Most of t he l ower vol t ages used i n t he TV may be der i ved f r om t he hor i zont al def l ect i on ci r cui t s. Somet i mes, t her e i s a separat e swi t chi ng power suppl y but t hi s woul d be t he except i on. Recti f i er / f i l t er capaci t or / r egul at or f r om AC l i ne pr ovi des t he B+ t o t he swi t chi ng power suppl y or hori zont al def l ect i on syst em. Degauss operat es of f of t he l i ne whenever power i s t ur ned on ( af t er havi ng been of f f or a f ew mi nut es) t o demagnet i ze t he CRT. Hori zont al def l ect i on. These ci r cui t s pr ovi de t he wavef orms needed t o sweep t he el ect r on beam i n t he CRT acr oss and back some 15, 734 t i mes per second ( f or NTSC) . The hor i zont al sync pul se f r om t he sync separ at or l ocks t he hor i zont al def l ecti on t o the vi deo si gnal . Ver t i cal def l ect i on. These ci r cui t s pr ovi de t he wavef or ms needed t o sweep t he el ect r on beam i n t he CRT f r om t op t o bot t om and back 60 t i mes per second ( f or NTSC) . The ver t i cal sync pul se f r om t he sync separ at or
l ocks t he ver t i cal def l ecti on t o t he vi deo si gnal . CRT hi gh vol t age ( al so par t of ( 2) ) . A moder n col or CRT r equi r es up t o 30 KV f or a cr i sp br i ght pi ct ur e. Rat her t han havi ng a t ot al l y separ at e power suppl y, near l y ever y TV on t he pl anet der i ves t he HV ( as wel l as many ot her vol t ages) f r om t he hor i zont al def l ect i on usi ng a speci al t r ansf or mer cal l ed a ' f l yback' or ' Li ne Out Put Tr ansf or mer ( LOPT) f or t hose of you on t he ot her si de of t he l ake. Tuner , I F, AGC, vi deo and audi o demodul at or s. I nput i s t he ant enna or cabl e si gnal and out put ar e baseband vi deo and audi o si gnal s. Ther e i s usual l y somepl ace i nsi de t he TV wher e l i ne l evel vi deo and audi o ar e pr esent but i t may not be accessi bl e f r om t he out si de of t he cabi net unl ess you pai d f or t he mor e expensi ve model wi t h t he A/ V opt i on. Very of t en, t he t uner i s a shi el ded met al box posi t i oned on t he bot t om r i ght ( as vi ewed f r om t he f r ont ) separ at e f r om t he mai n ci r cui t boar d. Somet i mes i t i s on t he mai n ci r cui t boar d. The I F sect i on may be i n ei t her pl ace. On ol der or cheap TVs wi t h a knob t uner , t hi s i s usual l y mount ed t o t he f r ont panel by i t sel f . Ther e are usual l y separ at e boxes f or t he VHF and UHF t uner s. Chr oma demodul at or . I nput i s t he baseband vi deo si gnal . Out put s ar e t he i ndi vi dual si gnal s f or t he r ed, gr een, and bl ue vi deo t o t he CRT. Vi deo dr i ver s ( RGB) . These ar e al most al ways l ocat ed on a l i t t l e ci r cui t boar d pl ugged di r ect l y ont o t he neck of t he CRT. They boost t he out put of t he chr oma demodul at or t o t he hundr ed vol t s or so needed t o dr i ve t he cat hodes of t he CRT. Sync separat or. I nput i s baseband vi deo. Out put i s hori zont al and ver t i cal sync pul ses to cont r ol t he def l ecti on ci r cui t s. Audi o ampl i f i er / out put . The l i ne l evel audi o i s ampl i f i ed t o dr i ve a set of speaker s. I f t hi s i s a st er eo TV, t hen t hese ci r cui t s must al so per f or m t he st er eo demul t i pl exi ng. System cont r ol . Most moder n TVs act ual l y use pr ogr am mi cr ocomput er t o per f or m al l user f r om t he f r ont panel and r emot e cont r ol . sophi st i cat ed. However , t hey do not f ai l of knobs and swi t ches and t hese ar e pr one
a mi cr ocont r ol l er - a f i xed i nt er f ace and cont r ol f unct i ons These ar e becomi ng i ncr easi ngl y of t en. Ol der TVs use a bunch t o wear and di r t .
Most pr obl ems occur i n t he hor i zont al def l ect i on and power suppl y sect i ons. These r un at r el at i vel y hi gh power l evel s and some component s r un hot . The hi gh vol t age sect i on i s pr one t o br eakdown and ar ci ng as a r esul t of hai r l i ne c r ac ks , humi di t y, di r t , et c . The t uner component s ar e usual l a l i ght eni ng st r i ke. However , sol i d st at e TVs, manuf act ur er s connect ors and shi el ds so t hat common even i n new set s. 3. 2)
y qui t e r el i abl e unl ess t he ant enna exper i ences i t s eems t hat even af t er 20+ year s of st i l l cannot r el i abl y sol der t he t uner bad sol der connect i ons i n t hese ar eas ar e
For mor e i nf or mat i on on TV t echnol ogy
The books l i st ed i n t he sect i on: Suggest ed r ef er ences i ncl ude addi t i onal
i nf ormat i on on t he t heory and i mpl ement at i on of t he t echnol ogy of t el evi si on st andar ds and TV r ecei ver s. For an on l i ne i nt r oduct i on t o TV and moni t or t echnol ogy, poi nt your web br owser t o t he Magnavox r ef er ence page at t he f ol l owi ng URL: ht t p: / / www. magnavox. com/ el ect r ef er ence/ el ect r ef er ence. ht ml Ther e you wi l l f i nd l i nks t o a number of ar t i cl es on t he basi c pr i nci pl es of oper at i on of CD pl ayer s, l aser di sc and opt i cal dr i ves, TVs, VCRs, camcor der s, l oudspeaker s, sat el l i t e r ecei ver s, and ot her consumer A/ V equi pment . Chapt er 4) 4. 1)
CRT Basi cs
Col or CRTs, Shadowmasks, Magnet i c Fi el ds, and Degauss
Al l col or CRTs ut i l i ze a shadowmask or aper t ur e gr i l l a f r act i on of an i nch ( 1/ 2 t ypi cal ) behi nd t he phosphor s cr een t o di r ect t he el ect r on beams f or t he red, gr een, and bl ue vi deo si gnal s t o t he pr oper phosphor dot s. Si nce t he el ect r on beams f or t he R, G, and B phosphors ori gi nat e f r om sl i ght l y di f f er ent posi t i ons (i ndi vi dual el ectr on guns f or each) and t hus arr i ve at sl i ght l y di f f er ent angl es, onl y t he pr oper phosphor s ar e exci t ed when t he pur i t y i s pr oper l y adj ust ed and t he necessar y magnet i c f i el d f r ee r egi on i s mai nt ai ned i nsi de t he CRT. Not e t hat pur i t y det er mi nes t hat t he cor r ect vi deo si gnal exci t es t he pr oper col or whi l e conver gence det er mi nes t he geomet r i c al i gnment of t he 3 col or s. Both ar e af f ect ed by magnet i c f i el ds. Bad pur i t y r esul t s i n mot t l ed or i ncor r ect col or s. Bad conver gence r esul t s i n col or f r i ngi ng at edges of char act er s or gr aphi cs. The shadowmask consi st s of a t hi n st eel or I nVar ( a f er r ous al l oy) wi t h a f i ne ar r ay of hol es - one f or each t r i o of phosphor dot s - posi t i oned about 1/ 2 i nch behi nd t he surf ace of t he phosphor scr een. Wi t h most CRTs, t he phosphors ar e ar r anged i n t r i angul ar f or mat i ons cal l ed t r i ads wi t h each of t he col or dot s at t he apex of t he t r i angl e. Wi t h many TVs and some moni t or s, t hey ar e arr anged as ver t i cal sl ot s wi t h t he phosphor s f or t he 3 col or s next t o one anot her . An aper t ur e gr i l l e, used excl usi vel y i n Sony Tr i ni t r ons ( and now t hei r cl ones as wel l ) , r epl aces t he shadowmask wi t h an ar r ay of f i nel y t ensi oned ver t i cal wi r es. Al ong wi t h ot her char act er i st i cs of t he aper t ur e gr i l l e appr oach, t hi s per mi t s a somewhat hi gher possi bl e br i ght ness t o be achi eved and i s mor e i mmune t o ot her pr obl ems l i ke l i ne i nduced moi r e and pur i t y changes due t o l ocal heat i ng causi ng di st or t i on of t he shadowmask. However , t her e ar e some di sadvant ages of t he aper t ur e gr i l l e desi gn: wei ght - a heavy suppor t st r uct ur e must be pr ovi ded f or t he t ensi oned wi r es ( l i ke a pi ano f r ame) . pr i ce ( pr opor t i onal t o wei ght ) . al ways a cyl i ndr i cal scr een ( t hi s may be consi der ed an advant age dependi ng on your pr ef er ence.
vi si bl e st abi l i zi ng wi r es whi ch may be obj ect i onabl e or unaccept abl e f or c er t ai n appl i c at i ons . Appar ent l y, t her e i s no known way ar ound t he need t o keep t he f i ne wi r es f r om vi br ati ng or changi ng posi t i on due t o mechani cal shock i n hi gh r esol ut i on t ubes and t hus al l Tr i ni t r on moni t or s r equi r e 1, 2, or 3 st abi l i zi ng wi r es ( dependi ng on t ube si ze) acr oss t he scr een whi ch can be see as ver y f i ne l i nes on br i ght i mages. Some peopl e f i nd t hese wi r es t o be obj ect i onabl e and f or some cr i t i cal appl i cat i ons, t hey may be unaccept abl e ( e. g. , medi cal di agnosi s) . 4. 2)
Why i s t he Shadowmask or Aper t ur e Gr i l l made of a magnet i c mat er i al ?
( From: J er oen St essen, ( st essenj @am. umc. ce. phi l i ps. nl ) ) The quest i on of t en ar i ses : Wel l , i f magnet i zat i on and t he need f or degauss i s a pr obl em, why not make t he shadowmask or aper t ur e gr i l l e f r om somet hi ng t hat i s non- magnet i c? The shadowmask MUST be made of magnet i c mat er i al ! Thi s may seem t o be undesi r abl e or count er i nt ui t i ve but r ead on: Toget her wi t h t he i nt er nal shi el di ng hood i t f or ms sor t of a cl osed space i n whi ch i t i s at t empt ed t o achi eve a f i el d- f r ee space. The pur pose of degaussi ng i s NOT t o demagnet i ze t he met al , but t o cr eat e a magnet i zat i on t hat compensat es f or t he eart h' s magnet i c f i el d. The SUM of t he t wo f i el ds must be near z er o! Degaussi ng coi l s cr eat e a str ong al t er nati ng magnet i c f i el d t hat gr adual l y decays to zer o. The ef f ect i s t hat t he pr esent ear t h magnet i c f i el d i s f r ozen i nt o t he magnet i c shi el di ng and t he f i el d i nsi de the shi el di ng wi l l be ( al most ) zer o. Non- zer o f i el d wi l l cause col our pur i t y er r or s. Now you wi l l under st and why a CRT must be degauss ed agai n af t er i t has been moved r el at i ve t o t he ear t h' s magnet i c f i el d. Thi s wi l l al so expl ai n why expensi ve comput er moni t or s on a swi vel pedest al have a manual degaussi ng but t on, you must pr ess i t ever y t i me af t er you have r ot at ed t he moni t or . The axi al component of t he magnet i c f i el d i s har der t o compensat e by means of degauss i ng. Bet t er compensat i on may be achi eved by means of a r ot at i on coi l ( around t he neck or around t he scr een) , t hi s r equi r es an adj ust ment t hat depends on l ocal magnet i c f i el d. CRT' s f or movi ng vehi cl es ( l i ke mi l i t ar y ai r pl anes) may be equi pped wi t h 6 coi l s t o achi eve zer o magnet i c f i el d i n al l di r ect i ons. They use magnet i c f i el d sensor s and act i ve compensat i on, t hus t hey don' t need any degaussi ng f unct i on. Thi s i s t oo expensi ve f or consumer equi pment . 4. 3)
Tubes f or al l Nat i ons
( From: J er oen St essen, ( st essenj @am. umc. ce. phi l i ps. nl ) ) CRT Manuf act ur er s actual l y make di f f er ent ver si TV' s f or t he nor t her n and sout her n hemi spher e, t ype. These are so- t o- say pr ecorr ect ed f or t he t hat t he t er m ' t ube' her e i ncl udes much of t he wel l - not j ust what i s i nsi de t he gl ass. )
ons of t hei r t ubes f or and somet i mes a 3r d neut r al uncompensat ed f i el d. ( Not e conver gence har dwar e as
I r emember when we export ed pr oj ect i on t el evi si ons f r om Bel gi um t o Aust r al i a, a coupl e of year s ago. They al l had t o be opened on arr i val t o re- adj ust t he rot at i on set t i ngs on t he conver gence panel , due t o t he di f f er ent magnet i c f i el d i n Aust r al i a. Pr oj ecti on TV' s don' t have degaussi ng ( t her e i s not hi ng t o degauss) , and t he cust omer can onl y adj ust r ed and bl ue shi f t , not r ot at i on. Our CRT appl i cat i on gr oup has a magnet i c cage. Thi s i s a wooden cube ( appr ox. 2 met er l ong si des) wi t h copper coi l s ar ound each of t he 6 sur f aces. Wi t h t hi s t hey can si mul ate t he ear t h magnet i c f i el d f or ever y pl ace on eart h ( as i ndi cat ed on a map on t he wal l ) . 4. 4)
Degauss i ng ( demagnet i zi ng) a CRT
Degaussi ng may be r equi r ed i f t her e ar e col or pur i t y pr obl ems wi t h t he di spl ay. On r ar e occasi ons, t her e may be geomet r i c di st ort i on caused by magnet i c f i el ds as wel l wi t hout col or pr obl ems. The CRT can get magnet i zed: I f t he TV or moni t or i s moved or even j ust r ot at ed. I f t her e has been a l i ght eni ng st r i ke near by. A f r i end of mi ne had a l i ght eni ng st r i ke near hi s house whi ch pr oduced al l of t he ef f ect s of t he EMP f r om a nucl ear bomb. I f a per manent magnet was br ought near t he scr een ( e. g. , ki d' s magnet or megawat t st er eo speaker s) . I f some pi ece of el ect r i cal or el ect r oni c equi pment wi t h unshi el ded magnet i c f i el ds i s i n t he vi ci ni t y of t he TV or moni t or . Degaussi ng shoul d be t he f i r st t hi ng at t empt ed whenever col or pur i t y pr obl ems ar e det ect ed. As not ed bel ow, f i r st t r y t he i nt er nal degauss ci r cui t s of t he TV or moni t or by power cycl i ng a f ew t i mes ( on f or a mi nut e, of f f or 30 mi nut es, on f or a mi nut e, et c. ) I f t hi s does not hel p or does not compl et el y cur e t he pr obl em, t hen you can t r y manual l y degaussi ng. Commer ci al CRT Degausser s ar e avai l abl e f r om part s di st r i but ors l i ke MCM El ect r oni cs and consi st of a hundr ed or so t ur ns of magnet wi r e i n a 6- 12 i nch coi l . They i ncl ude a l i ne cor d and moment ar y swi t ch. You f l i p on t he swi t ch, and br i ng t he coi l t o wi t hi n sever al i nches of t he scr een f ace. Then you sl owl y dr aw t he cent er of t he coi l t owar d one edge of t he screen and t r ace t he peri met er of t he screen f ace. Then r et ur n t o t he or i gi nal posi t i on of t he coi l bei ng f l at agai nst t he cent er of t he scr een. Next, sl owl y decr ease t he f i el d t o zer o by backi ng st r ai ght up across t he room as you hol d t he coi l . When you ar e f ar t her t han 5 f eet away you can r el ease t he l i ne swi t ch. The key wor d her e i s SLOW. Go t oo f ast and you wi l l f r eeze t he i nst ant aneous i nt ensi t y of t he 50/ 60 Hz AC magnet i c f i el d var i at i on i nt o t he f er r ous c omponent s of t he CRT and may make t he pr obl em wor se. I t l ooks r eal l y cool t o do t hi s whi l e t he CRT i s power ed. l ove t he col or ef f ects.
The ki ds wi l l
Bul k t ape er aser s, t ape head degausser s, open f r ame t r ansf or mer s, and t he
ass- end of a wel l er sol der i ng gun can be used as CRT demagnet i zer s but i t j ust t akes a l i t t l e l onger . ( Be car ef ul not t o scr at ch t he screen f ace wi t h anyt hi ng shar p. ) I t i s i mper at i ve t o have t he CRT r unni ng when usi ng t hese whi mpi er appr oaches, so t hat you can see wher e t her e ar e st i l l i mpur i t i es. Never r el ease t he power swi t ch unt i l you' r e 4 or 5 f eet away f r om t he screen or you' l l have t o st ar t over . I ' ve never known of anyt hi ng bei ng damaged by excess manual degauss i ng t hough I woul d r ecommend keepi ng r eal l y power f ul bul k t ape er aser s t ur ned degausser s a coupl e of i nches f r om t he CRT. I f an AC degaussi ng coi l or subst i t ut e i s unavai l abl e, I have even done degaussed wi t h a per manent magnet but t hi s i s not r ecommended si nce i t i s mor e l i kel y t o make t he pr obl em wor se t han bet t er . However , i f t he di spl ay i s unusabl e as i s, t hen usi ng a smal l magnet can do no har m. ( Don' t use a 20 pound speaker or magnet r on magnet as you may r i p t he shadowmask r i ght out of t he CRT - wel l at l east di st or t i t beyond r epai r . What I have i n mi nd i s somet hi ng about as power f ul as a r ef r i ger at or magnet . ) Keep degaussi ng f i el ds away f r om magnet i c medi a. I t i s a good i dea t o avoi d degaussi ng i n a r oom wi t h f l oppi es or back- up t apes. When r emovi ng medi a f r om a r oom r emember t o check desk dr awer s and manual s f or st r ay f l oppi es , t oo. I t i s unl i kel y t hat you coul d act ual l y af f ect magnet i c medi a but bet t er saf e t han sor r y. Of t he devi ces ment i oned above, onl y a bul k er aser or st r ong per manent magnet ar e l i kel y t o have any ef f ect - and t hen onl y when at ext r emel y cl ose r ange ( di r ect cont act wi t h medi a cont ai ner ) . Al l col or CRTs i ncl ude a bui l t - i n degaussi ng coi l wr apped around the per i met er of t he CRT f ace. These ar e act i vat ed each t i me t he CRT i s power ed up col d by a 3 t ermi nal t hermi st er devi ce or ot her cont r ol ci r cui t r y. Thi s i s why i t i s of t en suggest ed t hat col or pur i t y pr obl ems may go away i n a f ew days. I t i sn' t a mat t er of t i me; i t ' s t he number of col d power ups t hat causes i t . I t t akes about 15 mi nut es of t he power bei ng of f f or each cool down cycl e. These bui l t - i n coi l s wi t h t her mal cont r ol ar e never as ef f ecti ve as ext er nal coi l s. 4. 5)
Why ar e i ndi r ect l y heat ed cat hodes used i n CRT
Her e ar e t hr ee r easons: The cat hode can be made of and/ or coat ed wi t h a mat er i al opt i mal f or emi t t i ng el ect r ons wi t hout r egar d t o i t s per f ormance as a heater . The separ at e cat hode and f i l ament can be el ect r i cal l y i sol at ed so t hat t he f i l ament vol t age and cat hode dr i ve si gnal , i f any, do not i nt er f er e. The cat hode can have an opt i mal shape f or t he appl i cat i on. Thi s woul d be par t i cul ar l y si gni f i cant f or CRTs. The spot on t he screen i s a r educed f ocused i mage of t he ef f ect i ve shape of t he emi t t i ng port i on of t he cat hode. 4. 6)
Why do TVs over scan?
( The f ol l owi ng i ncl udes mat er i al f r om: J er oen St ess en ( st ess enj @am. nl vxe1. umc. ce. phi l i ps. nl ) )
Q: TVs ar e al ways set up t o gener at e a pi ct ur e whi ch i s 10- 15 percent l ar ge t han t he vi si bl e f ace of t he CRT. Why? I n t he earl y days of TV, t hi s was pr obabl y done t o make t he desi gn easi er . Component t ol er ances and power l i ne vol t age f l uct uat i ons woul d be masked even i f t hey caused changes i n pi ct ur e si ze. Ther e cer t ai nl y i s al most no r eason t oday t o have any mor e t han a coupl e of per cent over scan. Most moder n TVs have ver y wel l r egul at ed power suppl i es and component val ues do not r eal l y dr i f t much. Comput er moni t or s, f or exampl e, are usual l y set up f or no over scan at al l so t hat t he ent i r e i mage i s vi si bl e. We ar e const ant l y r emi nded of t hat , now t hat we ar e bui l di ng TV' s wi t h VGA i nput s ( PD5029C1 i n t he USA, US$ 2000) . Thi s mi xed appl i cat i on has over sc an i n TV mode and under scan i n VGA mode. Geomet r y adj ust ment i s qui t e cri t i cal i f you see bor der - on- bor der . Unf ort unat el y, TV' s t oo l i t t l e over scan sear ch) t hen one ( bl Vi ewer s do not l i ke
may be good but VCR' s cer t ai nl y ar e not . I f you have and t hen put t he VCR i n any f eat ur e mode ( l i ke pi ct ur e ack) pi ct ur e edge may become vi si bl e. Bad f or m. t hi s.
Whi l e desi gn consi derat i ons may have been t he or i gi nal r eason f or overs can, now i t has become accept ed as a def act o st andar d, and br oadcast er s ar e count i ng on t he over scan bei ng a cer t ai n per cent age. One wonder s whet her i t wi l l ever change or whet her t hi s r eal l y mat t er s. I suppose when we have t r ue f l at panel di gi t al l y addr essed di spl ays, we mi ght have 0% over scan. At t he J apan El ect r oni cs Show al l t he si gns are poi nt ed t owar d f l at panel di spl ays so maybe I wi l l not have t o hol d your br eat h f or much l onger . Physi cal l y, as wi t h an LCD di spl ay on a l apt op comput er , t her e wi l l be 0% overs can ( no need t o bui l d t he ext r a pi xel s) but t hat doesn' t mean t hat al l 480 l i nes wi l l be vi s i bl e. 4. 7)
Scr at ches i n CRT f ace
Mi nor scr at ches can be removed wi t h J ewel er ' s r ouge or si mi l ar ul t r a f i ne abr asi ve. J ewel er ' s Rouge i s t he same st uf f t hat i s used i n t he f i nal pol i shi ng of l enses and mi r r or s so i t makes f or a f i ne f i ni sh. However , any ki nd of scr atch deep enough t o be f el t wi l l not yi el d t o t hi s appr oach. WARNI NG: any ki nd of deep scr at ch on a CRT shoul d be consi der ed a ser i ous saf et y hazar d. Thi s may be even mor e of a concer n f or moder n CRTs t hat have ' i nt egr al i mpl osi on pr ot ect i on' - t hat st eel band ar ound t he out si de' . Ol der CRTs used ei t her ( 1) a separ ate saf et y shi el d - t hat l ami nat ed gl ass pl at e i n f r ont of your gr andmom' s TV - or ( 2) a second cont our ed gl ass panel bonded t o t he act ual t ube f ace. I n bot h of t hese cases, t he second panel i s st r i ct l y pr ot ect i ve and ser ves no st r uct ur al pur pose. Ther ef or e, any damage t o i t does not compr omi se t he t ube i n any way. I n t he case of moder n CRTs, t he st eel band i n conj unct i on wi t h t he basi c t ube envel ope i s used t o mai nt ai n t he i nt egr i t y of t he over al l CRT. Any damage si gni f i cant l y decr eases t he st r engt h and i ncr eases t he r i sk of CRT i mpl osi on.
BTW, scr at ches i n t he CRT have absol ut el y no ef f ect on X- r ay emi ssi on. X- r ays ar e bl ocked l ong bef or e t hey come anywher e near t he sur f ace and gl ass has ver y l i t t l e ef f ect on t hei r di r ect i on. Any scrat ch deep enough t o have any det ect abl e ef f ect on X- r ay emi ssi on ( act ual l y, i t woul d need t o be an i nch deep gouge) woul d have caused t he t ube t o i mpl ode. Chapt er 5) 5. 1)
TV Pl acement and Pr event i ve Mai nt enance
Gener al TV pl acement consi der at i ons
Pr oper car e of a TV does not r equi r e much. Fol l owi ng t he r ecommendat i ons bel ow wi l l assur e l ong l i f e and mi ni mi ze repai r s: Subdued l i ght i ng i s pr ef er r ed f or best vi ewi ng condi t i ons at t empt t o t el l you how t o ar r ange your r oom!
but I wi l l not
Locat e t he TV away f r om ext r emes of hot and col d. Avoi d damp or dust y l ocat i ons i f possi bl e. ( Ri ght you say, keep dr eami ng! ) Al l ow adequat e vent i l at i on - TVs use mor e power t han any of your ot her A/ V component s. Heat bui l dup t akes i t s t ol l on el ect r oni c component s. Leave at l east 3 i nches on t op and si des f or ai r ci r cul at i on i f t he ent er t ai nment cent er does not have a wi de open back panel . Do not pi l e ot her component s l i ke VCRs on t op of t he TV i f possi bl e ( see bel ow) . Do not put anyt hi ng on t op of t he TV t hat mi ght bl ock t he vent i l at i on gr i l l i n t he r ear or t op of t he cover . Thi s i s t he maj or avenue f or t he convect i on needed t o cool i nt er nal component s. I f possi bl e, l ocat e t he VCR away f r om t he TV. Some VCRs ar e par t i cul arl y sensi t i ve t o i nt er f er ence f r om t he TV' s ci r cui t r y and whi l e t hi s won' t usual l y damage anyt hi ng, i t may make f or l ess t han opt i mal per f or mance due t o RF i nt erf er ence. The r ever se i s somet i mes t r ue as wel l . I f possi bl e, l ocat e your comput er moni t or away f r om t he TV. I nt er act i on of t he el ect r omagnet i c f i el ds of t he def l ect i on syst ems may resul t i n one or bot h di spl ays j i ggl i ng, wi ggl i ng, or vi br at i ng. Locat e l oudspeaker s and ot her sour ces of magnet i c f i el ds at l east a coupl e of f eet f r om t he TV. Thi s wi l l mi ni mi ze t he possi bi l i t y of col or pur i t y or geomet r y pr obl ems. Make sur e al l i nput - out put vi deo and audi o connect i ons ar e t i ght and secur e t o mi ni mi ze i nt ermi t t ent or noi sy pi ct ur es and sound. Use pr oper hi gh qual i t y cabl e onl y l ong enough t o make connect i ons conveni ent l y. Fi nal l y, st or e vi deo casset t es wel l away f r om al l el ect r oni c equi pment i ncl udi ng and especi al l y l oudspeaker s. Heat and magnet i c f i el ds wi l l r api dl y t ur n your pri cel ess vi deo col l ect i on i nt o so much t r ash. The oper at i on of t he TV depends on magnet i c f i el ds f or beam def l ect i on. Enough sai d. 5. 2)
Pr event i ve mai nt enance
Pr event i ve mai nt enance f or a TV i s pret t y si mpl e - j ust keep t he case cl ean and f r ee of obst r uct i ons. Cl ean t he scr een wi t h a sof t cl ot h j ust dampened wi t h wat er and at most , mi l d det er gent . DO NOT use anyt hi ng so wet t hat
l i qui d may seep i nsi de of t he set ar ound t he edge of t he pi ct ur e t ube - you coul d end up wi t h a ver y expensi ve r epai r bi l l when t he l i qui d shor t s out t he mai n ci r cui t boar d l ur ki ng j ust bel ow. I f t he set has a pr ot ect i ve f l at gl ass f acepl at e, t her e i s usual l y an easy way ( on newer set s wi t h t hi s t ype of pr otect i on) of r emovi ng i t t o get at t he i nner f ace of t he CRT. Cl ean bot h t he CRT and t he pr ot ect i ve gl ass wi t h a sof t damp cl ot h and dr y t hor oughl y. I f you have not cl eaned t he scr een f or qui t e a whi l e, you wi l l be amazed at t he amount of bl ack gr i me t hat col l ect s due t o t he st at i c bui l dup f r om t he hi gh vol t age CRT suppl y. I n r eal l y dust y si t uat i ons, per i odi cal l y vacuumi ng i nsi de t he case and t he use of cont act cl eaner f or t he cont r ol s mi ght be a good i dea but r eal i st i cal l y, you wi l l not do t hi s so don' t wor r y about i t . Chapt er 6) 6. 1)
TV Tr oubl eshoot i ng
Saf et y
TVs and comput er or vi deo moni t or s ar e among t he mor e danger ous of consumer el ect r oni cs equi pment when i t comes t o ser vi ci ng. ( Mi cr owave ovens ar e pr obabl y t he most hazar dous due t o hi gh vol t age at hi gh power . ) Ther e ar e t wo ar eas whi ch have par t i cul ar l y nast y el ect r i cal danger s: t he non- i sol at ed l i ne power suppl y and t he CRT hi gh vol t age. Maj or par t s of near l y al l moder n TVs and many comput er moni t or s ar e di r ect l y connect ed t o t he AC l i ne - t here i s no power t r ansf ormer t o pr ovi de t he essent i al barr i er f or s af et y and t o mi ni mi ze t he r i sk of equi pment damage. I n t he maj or i t y of desi gns, t he l i ve par t s of t he TV or moni t or ar e l i mi t ed t o the AC i nput and l i ne f i l t er , degauss ci r cui t , br i dge r ecti f i er and mai n f i l t er capaci t or ( s) , l ow vol t age ( B+) r egul at or ( i f any) , hor i zont al out put t r ansi st or and pr i mary si de of t he f l yback ( LOPT) t r ansf or mer , and part s of t he st ar t up ci r cui t and st andby power suppl y. The f l yback gener at es most of t he ot her vol t ages used i n t he uni t and pr ovi des an i sol at i on bar r i er so t hat t he si gnal ci r cui t s ar e not l i ne connect ed and saf er . Si nce a br i dge r ect i f i er i s gener al l y used i n t he power suppl y, bot h di r ect i ons of t he pol ar i zed pl ug r esul t i n danger ous condi t i ons and an i sol at i on t r ansf or mer r eal l y shoul d be used - t o pr ot ect you, your t est equi pment , and t he TV, f r om ser i ous damage. Some TVs do not have any i sol at i on bar r i er what soever - t he ent i r e chassi s i s l i ve. These ar e par t i c ul ar l y nas t y . The hi gh vol t age t o t he CRT, whi l e 200 t i mes gr eat er t han t he l i ne i nput , i s not near l y as danger ous f or sever al r easons. Fi r st , i t i s pr esent i n a ver y l i mi t ed ar ea of t he TV or moni t or - f r om t he out put of t he f l yback t o t he CRT anode vi a t he f at r ed wi r e and suct i on cup connect or. I f you don' t need t o r emove t he mai nboar d or r epl ace t he f l yback or CRT, t hen l eave i t al one and i t shoul d not bi t e. Fur t her more, whi l e t he shock f r om t he HV can be qui t e pai nf ul due t o t he capaci t ance of t he CRT envel ope, i t i s not near l y as l i kel y t o be l et hal si nce t he cur r ent avai l abl e f r om t he l i ne connect ed power suppl y i s much gr eat er . 6. 2)
Saf et y Gui del i nes
These gui del i nes ar e t o pr ot ect you f r om pot ent i al l y deadl y el ect r i cal shock hazar ds as wel l as t he equi pment f r om acci dent al damage.
Not e t hat t he danger t o you i s not onl y i n your body pr ovi di ng a conduct i ng pat h, par t i cul ar l y t hr ough your heart . Any i nvol unt ar y muscl e cont r act i ons caused by a shock, whi l e per haps har ml ess i n t hemsel ves, may cause col l at er al damage - t her e ar e many shar p edges i nsi de t hi s t ype of equi pment as wel l as ot her el ect r i cal l y l i ve par t s you may cont act acci dent al l y. The pur pose of t hi s set of gui del i nes i s not t o f r i ght en you but r at her t o make you aware of t he appr opr i at e pr ecaut i ons. Repai r of TVs, moni t or s, mi cr owave ovens, and ot her consumer and i ndust r i al equi pment can be bot h r ewar di ng and economi cal . J ust be sur e t hat i t i s al so saf e! Don' t wor k al one - i n t he event of an emer gency anot her per son' s pr esence may be essent i al . Al ways keep one hand i n your pocket when anywher e ar ound a power ed l i ne- connect ed or hi gh vol t age syst em. Wear r ubber bot t om shoes or sneaker s. Don' t wear any j ewel r y or other ar t i cl es t hat coul d acci dent al l y cont act ci r cui t r y and conduct cur r ent , or get caught i n movi ng part s. Set up your wor k ar ea away f r om possi bl e gr ounds t hat you may acci dent al l y cont act. Know your equi pment : TVs and moni t or s may use par t s of t he met al chass i s as gr ound r et ur n yet t he chassi s may be el ect r i cal l y l i ve wi t h r espect t o t he ear t h gr ound of t he AC l i ne. Mi cr owave ovens use t he chassi s as gr ound r et ur n f or t he hi gh vol t age. I n addi t i on, do not assume t hat t he chassi s i s a sui t abl e gr ound f or your t est equi pment ! I f ci r cui t boar ds need t o be r emoved f r om t hei r mount i ngs, put i nsul at i ng mat er i al bet ween t he boar ds and anyt hi ng t hey may shor t t o. Hol d t hem i n pl ace wi t h st r i ng or el ectr i cal t ape. Pr op t hem up wi t h i nsul at i on st i cks pl ast i c or wood. I f you need t o pr obe, sol der , or ot her wi se t ouch ci r cui t s wi t h power of f , di schar ge (acr oss) l ar ge power suppl y f i l t er capaci t or s wi t h a 2 W or gr eat er r esi st or of 100- 500 ohms/ V appr oxi mat e val ue ( e. g. , f or a 200 V capaci t or, use a 20K- 100K ohm r esi st or ) . Moni t or whi l e di schar gi ng and/ or ver i f y t hat t her e i s no r esi dual char ge wi t h a sui t abl e vol t met er . I n a TV or moni t or , i f you ar e r emovi ng t he hi gh vol t age connect i on t o t he CRT ( t o r epl ace t he f l yback t r ansf or mer f or exampl e) f i r st di schar ge t he CRT cont act ( under t he i nsul at i ng cup at t he end of t he f at r ed wi r e) . Use a 1M- 10M ohm 1W or gr eater wat t age r esi st or on t he end of an i nsul at i ng st i ck or t he pr obe of a hi gh vol t age met er . Di schar ge t o t he met al f r ame whi ch i s connect ed t o t he out si de of t he CRT. For TVs and moni t or s i n par t i cul ar , t her e i s t he addi t i onal danger of CRT i mpl osi on - t ake car e not t o bang t he CRT envel ope wi t h your t ool s. An i mpl osi on wi l l scat t er shar ds of gl ass at hi gh vel oci t y i n ever y di r ect i on. Ther e ar e sever al t ons of f or ce at t empt i ng t o crush t he t ypi cal CRT. Al ways wear eye pr ot ect i on. Connect / di sconnect any t est l eads wi t h t he equi pment unpower ed and unpl ugged. Use cl i p l eads or sol der t empor ar y wi r es t o r each cr amped l oc at i ons or d i f f i c ul t t o ac ces s l oc at i ons .
I f you must pr obe l i ve, of t he t est pr obes t o coul d cause damage t o met er or scope t o t he pr obe wi t h one hand.
put el ect r i cal t ape over al l but t he l ast 1/ 16 avoi d t he possi bi l i t y of an acci dent al shor t whi ch var i ous component s. Cl i p t he r ef er ence end of t he appr opr i at e gr ound r et ur n so t hat you need t o onl y
Per f or m as many t est s as possi bl e wi t h power of f and t he equi pment unpl ugged. For exampl e, t he semi conduct or s i n t he power suppl y sect i on of a TV or moni t or can be t est ed f or s hort ci r cui t s wi t h an ohmmet er . Use an i sol at i on t r ansf ormer i f t her e i s any chance of cont act i ng l i ne connect ed ci r cui t s. A Var i ac( t m) i s not an i sol at i on t r ansf or mer ! The use of a GFCI ( Gr ound Faul t Ci r cui t I nt er r upt er ) pr ot ect ed out l et i s a good i dea but wi l l not pr ot ect you f r om shock f r om many poi nt s i n a l i ne connect ed TV or moni t or , or t he hi gh vol t age si de of a mi cr owave oven, f or exampl e. ( Not e however , t hat , a GFCI may nui sanse t r i p at power - on or at ot her r andom t i mes due t o l eakage pat hs ( l i ke your scope pr obe gr ound) or t he hi ghl y capaci t i ve or i nduct i ve i nput char act er i st i cs of l i ne power ed equi pment . ) A f use or ci r cui t br eaker i s t oo sl ow and i nsensi t i ve t o pr ovi de any pr ot ect i on f or you or i n many cases, your equi pment . However , t hese devi ces may save your scope pr obe gr ound wi r e shoul d you acci dent al l y connect i t t o a l i ve c has si s . Don' t at t empt r epai r wor k when you ar e t i r ed. Not onl y wi l l you be mor e car el ess, but your pr i mar y di agnost i c t ool - deduct i ve r easoni ng - wi l l not be oper at i ng at f ul l capaci t y. Fi nal l y, never assume anythi ng wi t hout checki ng i t out f or your sel f ! Don' t t ake short cut s! 6. 3)
Tr oubl eshoot i ng t i ps
Many pr obl ems have si mpl e sol ut i ons. Don' t i mmedi at el y assume t hat your pr obl em i s some combi nat i on of esot er i c compl ex convol ut ed f ai l ur es. For a TV, i t may j ust be a bad connect i on or bl own f use. Remember t hat t he pr obl ems wi t h t he most cat ast r ophi c i mpact on oper at i on l i ke a dead TV usual l y have t he si mpl est sol ut i ons. The ki nd of pr obl ems we woul d l i ke t o avoi d at al l cost s ar e t he ones t hat ar e i nt er mi t t ent or di f f i cul t t o r epr oduce: t he occasi onal i nt er f er ence or a TV t hat r ef uses t o pl ay ' St ar Tr ek Voyager ' . I f you get st uck, sl eep on i t . Somet i mes, j ust l et t i ng t he pr obl em bounce around i n your head wi l l l ead t o a di f f er ent mor e successf ul appr oach or sol ut i on. Don' t wor k when you ar e r eal l y t i r ed - i t i s bot h danger ous ( especi al l y wi t h r espect t o TVs) and most l y non- pr oduct i ve ( or pos si bl y des t r uc t i ve) . Whenever wor ki ng on pr eci si on equi pment , make copi ous not es and di agr ams. You wi l l be et er nal l y gr at ef ul when t he t i me comes t o r eass embl e t he uni t . Most connect ors ar e keyed agai nst i ncor r ect i nser t i on or i nt er change of cabl es, but not al ways. Appar ent l y i dent i cal scr ews may be of di f f er i ng l engt hs or have sl i ght l y di f f er ent t hr ead t ypes. Li t t l e par t s may f i t i n mor e t han one pl ace or or i ent ati on. Et c. Et c. Pi l l bot t l es, f i l m cani st er s, and pl ast i c i ce cube t r ays come i n handy f or sort i ng and st or i ng scr ews and ot her smal l part s af t er di sassembl y. Thi s i s par t i cul ar l y t r ue i f you have r epai r s on mul t i pl e pi eces of equi pment
under way si mul t aneousl y. Sel ect a wor k ar ea whi ch i s wi de open, wel l l i ght ed, and wher e dr opped par t s can be l ocat ed - not on a deep pi l e shag r ug. The best l ocat i on wi l l al so be r el at i vel y dust f r ee and al l ow you t o suspend your t r oubl eshoot i ng t o eat or sl eep or t hi nk wi t hout havi ng t o pi l e ever yt hi ng i nt o a car dboard box f or st or age. Anot her consi der at i on i s ESD - El ect r o- St at i c Di scharge. Some ( l i ke I Cs) i n a TV ar e vul ner abl e t o ESD. Ther e i s no need t o but t aki ng reasonabl e pr ecaut i ons such as get t i ng i nt o t he habi t he chassi s f i r st bef or e any of t he el ect r oni c component s i s a
component s go overboar d t of t ouchi ng good pr act i ce.
A basi c set of pr eci si on hand tool s wi l l be al l you need t o di sassembl e a TV and per f or m most adj ust ment s. These do not need t o be r eal l y expensi ve but poor qual i t y t ool s ar e wor se t han usel ess and can cause damage. Needed t ool s i ncl ude a sel ect i on of Phi l i ps and st r ai ght bl ade screwdr i ver s, socket dr i ver s, needl enose pl i er s, wi r e cut t er s, t weezer s, and dent al pi cks. For adj ust ment s, a mi ni at ur e ( 1/ 16 bl ade) scr ewdr i ver wi t h a non- met al l i c t i p i s desi r abl e bot h t o pr event t he pr esence of met al f r om al t er i ng t he el ectr i cal pr oper t i es of t he ci r cui t and t o mi ni mi ze the possi bi l i t y of shor t i ng somet hi ng f r om acci dent al cont act wi t h t he ci r cui t r y. A set of pl ast i c al i gnment t ool s wi l l be usef ul f or maki ng adj ust ment s t o coi l s and RF t r ansf or mer s. A l ow power ( e. g. , 25 W) f i ne t i p sol der i ng i r on and f i ne r osi n cor e sol der wi l l be needed i f you shoul d need t o di sconnect any sol der ed wi r es ( on pur pose or by acci dent ) or r epl ace sol der ed component s. A hi gher power i r on or s mal l sol der i ng gun wi l l be needed f or deal i ng wi t h l ar ger component s. For t her mal or war mup pr obl ems, a can of ' col d spr ay' or ' ci r cui t chi l l er ' ( t hey ar e t he same) and a heat gun or bl ow dr yer come i n handy t o i dent i f y component s whose char act er i st i cs may be dr i f t i ng wi t h t emper at ur e. Usi ng t he ext ensi on t ube of t he spr ay can or maki ng a car dboar d nozzl e f or t he heat gun can pr ovi de ver y pr eci se cont r ol of whi ch component s you are af f ect i ng. For i nf o on usef ul chemi cal s, adhesi ves, and l ubr i cant s, see Repai r Br i ef s, an I nt r oducti on as wel l as ot her document s avai l abl e at t hi s si t e. 6. 4)
Test equi pment
Don' t st ar t wi t h the el ect r oni c t est equi pment , st ar t wi t h some anal yti cal t hi nki ng. Your power s of obser vat i on ( and a l i t t l e exper i ence) wi l l make a good st ar t . Your bui l t i n senses and t hat st uf f bet ween your ear s r epr esent s t he most i mpor t ant t est equi pment you have. However , some t est equi pment wi l l be needed: Mul t i t est er ( DMM or VOM) - Thi s i s essent i al f or checki ng of power suppl y vol t ages and vol t ages on t he pi ns of I Cs or ot her component s - servi ce l i t erat ur e l i ke t he SAMs Phot of act s descri bed el sewher e i n t hi s document i ncl ude vol t age measur ement s at near l y ever y ci r cui t t i e poi nt f or pr oper l y f unct i oni ng equi pment . The mul t i t est er wi l l al so be used t o check component s l i ke t r ansi st or s, r esi st or s, and capaci t or s f or cor r ect val ue and f or shor t s or opens. You do not need a f ancy i nst r ument . A basi c DMM - as l ong as i t i s rel i abl e - wi l l suf f i ce f or most t r oubl eshoot i ng. I f you want one t hat wi l l l ast f or many year s, go wi t h a Fl uke. However ,
even t he mi d r ange DMMs f r om Radi o Shack have pr oven t o be r el i abl e and of accept abl e accur acy. For s ome ki nds of measur ement s - t o deduce t r ends f or exampl e - an anal og VOM i s pr ef er r ed ( t hough some DMMs have a bar gr aph scal e whi ch al most as good) . Osci l l oscope - Whi l e many pr obl ems can be deal t wi t h usi ng j ust a mul t i met er , a ' scope wi l l be essent i al as you get more i nt o advanced t r oubl eshoot i ng. Basi c r equi r ement s ar e: dual t r ace, 10- 20 MHz mi ni mum ver t i cal bandwi dt h, del ayed sweep desi r abl e but not essent i al . A good set of pr oper 10x/ 1x pr obes. Hi gher vert i cal bandwi dt h i s desi r abl e but most consumer el ect r oni cs wor k can be done wi t h a 10 MHz scope. A st or age scope or di gi t al scope mi ght be desi r abl e f or cer t ai n t asks but i s by no means essent i al f or basi c t r oubl eshoot i ng. I woul d r ecommend a good used Tekt r oni x or HP sc ope over a new scope of al most any ot her br and. You wi l l usual l y get mor e scope f or your money and t hese t hi ngs l ast al most f or ever . My ' good' scope i s t he mi l i t ar i zed ver si on ( AN/ USM- 281A) of t he HP180 l ab scope. Thi s has a dual channel 50 MHz ver t i cal pl ugi n and a del ayed sweep hor i zont al pl ugi n. I have seen t hese goi ng f or under $300 f r om sur pl us out f i t s. For a l i t t l e mor e money, you can get a Tek 465 100 Mhz scope ( $400- 700) whi ch wi l l suf f i ce f or al l but t he most demandi ng ( r ead: RF or hi gh s peed di gi t al ) r epai r s . A vi deo si gnal sour ce - bot h RF and baseband ( RCA j acks) . Unl ess you ar e t r oubl eshoot i ng t uner or vi deo/ audi o i nput pr obl ems, ei t her one wi l l suf f i ce. RF sour ces i ncl ude a pai r of r abbi t ear s or an out door ant enna, a cabl e connect i on, or a VCR wi t h a wor ki ng RF modul at or . Thi s wi l l be mor e conveni ent t han an ant enna connect i on and wi l l per mi t you t o cont r ol t he pr ogr am mat er i al . I n f act , maki ng some t est t apes usi ng a camcor der or vi deo camer a t o r ecor d stat i c t est pat t er ns wi l l al l ow you f ul l cont r ol of what i s bei ng di spl ayed and f or how l ong. Col or bar / dot / cr osshat ch si gnal gener at or . Thi s i s a usef ul pi ece of equi pment i f you ar e doi ng a l ot of TV or moni t or r epai r and need t o per f or m CRT conver gence and chr oma adj ust ment s. However , t her e are al t er nat i ves t hat ar e al most as good: a VHS r ecordi ng of t hese t est pat t er ns wi l l work f or TVs. A PC pr ogr ammed t o out put a sui t abl e set of t est pat t er ns wi l l be f i ne f or moni t or s ( and TVs i f you can set up t he vi deo car d t o pr oduce an NTSC/ PAL si gnal . Thi s can be put t hr ough a VCR t o gener at e t he RF ( Channel 3/ 4) i nput t o your TV i f i t does not have di r ect vi deo i nput s ( RCA j acks) . 6. 5)
I ncr edi bl y Handy wi dget s
These ar e t he l i t t l e gadget s and homemade t est er s t hat ar e usef ul f or many r epai r si t uat i ons. Her e ar e j ust a f ew of t he most basi c: Ser i es l i ght bul b f or cur r ent l i mi t i ng dur i ng t he t est i ng of TVs, moni t or s, swi t chi ng power suppl i es, audi o power ampl i f i er s, et c. I bui l t a dual out l et box wi t h t he out l et s wi r ed i n ser i es so t hat a l amp can be pl ugged i nt o one out l et and t he devi ce under t est i nt o t he ot her . For added ver sat i l i t y, add a regul ar out l et and ' ki l l ' swi t ch usi ng a quad box i nst ead. The use of a ser i es l oad wi l l pr event your expensi ve r epl acement par t l i ke a hor i zont al out put t r ansi st or f r om bl owi ng i f t her e i s sti l l some f aul t i n t he ci r cui t you have f ai l ed t o l ocat e. A Var i ac.
I t doesn' t need t o be l arge - a 2 A Vari ac mount ed wi t h
a swi t ch, out l et and f use wi l l suf f i ce f or most t asks. However , a 5 amp or l ar ger Var i ac i s desi r abl e. I f you wi l l be t r oubl eshoot i ng 220 VAC equi pment i n t he US, t her e ar e Var i acs t hat wi l l out put 0- 240 VAC f r om a 115 VAC l i ne ( j ust make sur e you don' t f or get t hat t hi s can easi l y f r y your 115 VAC equi pment . ) By varyi ng t he l i ne vol t age, not onl y can you br i ng up a newl y r epai r ed TV gr adual l y t o make sur e t her e ar e no pr obl ems but you can al so eval uat e behavi or at l ow and hi gh l i ne vol t age. Thi s can gr eat l y ai d i n t r oubl eshoot i ng power suppl y pr obl ems. WARNI NG: a Var i ac i s not an i sol at i on t r ansf or mer and does not hel p wi t h respect t o saf et y. You need an i sol at i on t r ansf or mer as wel l . I sol at i on t r ansf or mer . Thi s i s ver y i mpor t ant f or saf el y wor ki ng on l i ve chassi s equi pment . Si nce al l moder n TVs use a l i ne connect ed power suppl y, i t i s essent i al . You can bui l d one f r om a pai r of si mi l ar power t r ansf or mer s back- t o- back ( wi t h t hei r hi ghest r at ed secondari es connect ed t oget her . I bui l t mi ne f r om a coupl e of si mi l ar ol d t ube t ype TV power t r ansf or mer s mount ed on a boar d wi t h an out l et box i ncl udi ng a f use. Thei r hi gh vol t age wi ndi ngs wer e connect ed t oget her . The unused l ow vol t age wi ndi ngs can be put i n ser i es wi t h t he pr i mar y or out put wi ndi ngs t o adj ust vol t age. Al t er nat i vel y, commer ci al l i ne i sol at i on t r ansf or mer s sui t abl e f or TV t r oubl eshoot i ng ar e avai l abl e f or l ess t han $100 - wel l wor t h ever y penny. Vari abl e i sol at i on t r ansf ormer. You don' t need t o buy a f ancy combi nat i on uni t . A Var i ac can be f ol l owed by a nor mal i sol at i on t r ansf or mer . ( The opposi t e or der al so wor ks. Ther e may be some subt l e di f f er ences i n l oad c apac i t y. ) . Degaussi ng coi l . Make or buy. The i nt er nal degaussi ng coi l sal vaged f r om a def unct TV doubl ed over t o hal f i t or i gi nal di amet er t o i ncr ease i t s s t r engt h i n s er i es wi t h a 200 W l i ght bul b f or c ur r ent l i mi t i ng wi l l wor k j ust f i ne. Or , buy one f r om a pl ace l i ke MCM El ect r oni cs - about $15 f or one sui t abl e f or al l but t he l ar gest TVs. Al so, see t he sect i on: Degauss i ng ( demagnet i zi ng) CRTs. 6. 6)
Saf e di schargi ng of capaci t or s i n TVs and vi deo moni t ors
I t i s essent i al - f or your saf et y and t o pr event damage t o t he devi ce under t est as wel l as your t est equi pment - t hat l arge or hi gh vol t age capaci t ors be f ul l y di schar ged bef or e measur ement s ar e made, sol der i ng i s at t empt ed, or t he ci r cui t r y i s t ouched i n any way. Some of t he l ar ge f i l t er capaci t or s commonl y f ound i n l i ne oper at ed equi pment st or e a pot ent i al l y l et hal char ge. Thi s doesn' t mean t hat ever y one of t he 250 capaci t or s i n your TV need t o be di schar ged ever y t i me you power of f and want t o make a measur ement . However , t he l arge mai n f i l t er capaci t ors and ot her capaci t or s i n t he power suppl i es shoul d be checked and di schar ged i f any si gni f i cant vol t age i s f ound af t er power i ng of f ( or bef or e any test i ng - some capaci t or s ( l i ke t he hi gh vol t age of t he CRT i n a TV or vi deo moni t or ) wi l l r et ai n a danger ous or at l east pai nf ul char ge f or days or l onger ! ) The t echni que I r ecommend i s t o use a hi gh wat t age r esi st or of about 100 ohms/ V of t he worki ng vol t age of t he capaci t or. Thi s wi l l pr event t he ar c- wel di ng associ at ed wi t h scr ewdr i ver di schar ge but wi l l have a shor t enough t i me const ant so t hat t he capaci t or wi l l dr op t o a l ow vol t age i n at most a f ew seconds ( dependent of cour se on t he RC t i me const ant and i t s ori gi nal vol t age) .
Then check wi t h a vol t met er t o be doubl e sur e. Bet t er yet , moni t or whi l e di schargi ng ( not needed f or t he CRT - di scharge i s near l y i nst ant aneous even wi t h mul t i - M ohm r esi st or ) . Obvi ousl y, make sur e t hat you are wel l i nsul at ed! For t he mai n capaci t or s i n a swi t chi ng power suppl y whi ch mi ght be 100 uF at 350 V t hi s woul d mean a 5K 10W r esi st or . RC=. 5 second. 5RC=2. 5 seconds. A l ower wat t age r esi st or can be used si nce t he t ot al ener gy i n not t hat great . The ci r cui t descr i bed bel ow can used t o pr ovi de a vi sual i ndi cat i on of pol ar i t y and char ge. For t he CRT, use a hi gh wat t age ( not f or power but t o hol d of f t he hi gh vol t age whi ch coul d j ump acr oss a t i ny 1/ 4 wat t j ob) r esi st or of a f ew M ohms di schar ged t o t he chassi s gr ound connect ed t o t he out si de of t he CRT - NOT SI GNAL GROUND ON THE MAI N BOARD as you may damage s ens i t i ve ci r cui t r y. The t i me const ant i s ver y shor t - a ms or so. However , r epeat a f ew t i mes t o be sur e. ( Usi ng a shor t i ng cl i p l ead may not be a bad i dea as wel l whi l e wor ki ng on t he equi pment - t her e have been t oo many st or i es of pai nf ul exper i ences f r om charge devel opi ng f or what ever r easons r eady t o bi t e when t he HV l ead i s r econnect ed. ) Not e t hat i f you ar e t ouchi ng t he l i t t l e boar d on t he neck of t he CRT, you may want t o di schar ge t he HV even i f you ar e not di sconnect i ng t he f at r ed wi r e - t he f ocus and scr een ( G2) vol t ages on t hat boar d ar e der i ved f r om t he CRT HV. I f you ar e not goi ng t o be r emovi ng t he CRT anode connect i on, r epl aci ng t he f l yback, or goi ng near t he component s on t he l i t t l e boar d on t he neck of t he CRT, I woul d j ust st ay away f r om t he f at r ed wi r e and what i t i s connect ed t o i ncl udi ng t he f ocus and scr een wi r es. Repeat edl y shovi ng a scr ewdr i ver under t he anode cap r i sks s cr at chi ng t he CRT envel ope whi ch i s somet hi ng you r eal l y do not want t o do. Agai n, al ways doubl e check wi t h a r el i abl e vol t met er ! Reasons t o use a r esi st or and not a scr ewdr i ver t o di scharge capaci t or s: I t wi l I t wi l I t wi l scar y
l not dest r oy screwdr i ver s and capaci t or t er mi nal s. l not damage t he capaci t or ( due t o t he cur r ent pul se) . l r educe your spouse' s st r ess l evel i n not havi ng t o hear t hose snaps and cr ackl es.
6. 7)
The ser i es l i ght bul b t r i ck
When power i ng up a TV ( or any ot her moder n el ect r oni c devi ces wi t h expensi ve power semi conduct or s) t hat has had wor k done on any power ci r cui t s, i t i s desi r abl e to mi ni mi ze t he chance of bl owi ng your newl y i nst al l ed par t s shoul d t her e st i l l be a f aul t . Ther e ar e t wo ways of doi ng t hi s: use of a Vari ac t o br i ng up t he AC l i ne vol t age gr adual l y and t he use of a ser i es l oad t o l i mi t cur r ent t o power semi conduct or s. Actual l y usi ng a ser i es l oad - a l i ght bul b i s j ust a r eadi l y avai l abl e cheap l oad - i s bet t er t han a Var i ac ( wel l bot h mi ght be bet t er st i l l ) si nce i t wi l l l i mi t c ur r ent t o ( hopef ul l y) non- des t r uc t i ve l evel s . What you want t o do i s l i mi t cur r ent t o t he cr i t i cal par t s - usual l y the hor i zont al out put t r ansi st or ( HOT) . Most of t he t i me you wi l l get away wi t h put t i ng i t i n ser i es wi t h t he AC l i ne. However , somet i mes, put t i ng a l i ght bul b di r ectl y i n t he B+ ci r cui t wi l l pr ovi de bet t er protecti on as i t wi l l
l i mi t t he cur r ent out of t he mai n f i l t er capaci t or s t o t he HOT. Act ual l y, an act ual power r esi st or i s pr obabl y bet t er as i t s r esi st ance i s const ant as opposed t o a l i ght bul b whi ch wi l l var y by 1: 10 f r om col d t o hot . The l i ght bul b, however , pr ovi des a ni ce vi sual i ndi cat i on of t he cur r ent dr awn by t he ci r cui t under t est . For exampl e: Ful l br i ght ness: shor t ci r cui t or ext r emel y heavy l oad - a f aul t pr obabl y i s s t i l l pr esent . I ni t i al l y br i ght but t hen s et t l es at r educ ed br i ght nes s : f i l t er c apac i t or s char ge, t hen l ower cur r ent t o r est of ci r cui t . Thi s i s what i s expect ed when t he equi pment i s oper at i ng normal l y. Ther e coul d st i l l be a pr obl em wi t h t he power ci r cui t s but i t wi l l pr obabl y not r esul t i n an i mmedi at e c at as t r ophi c f ai l ur e. Pul sat i ng: power suppl y i s t r yi ng t o come up but shut t i ng down due t o over cur r ent or over vol t age condi t i on. Thi s coul d be due t o a cont i nui ng f aul t or t he l i ght bul b may be t oo smal l f or t he equi pment . The f ol l owi ng ar e suggest ed st ar t i ng wat t ages: 40 W bul b f or VCR or l apt op comput er swi t chi ng power suppl i es. 100 W bul b f or smal l ( i . e. , B/ W or 13 i nch col or ) TVs. 150- 200 W bul b f or l ar ge col or or pr oj ect i on TVs. Dependi ng on t he power r at i ng of t he equi pment , t hese wat t ages may need t o be i ncreased. However , st ar t l ow. I f t he bul b l i ght s at f ul l br i ght ness, you know t her e i s st i l l a maj or f aul t . I f i t f l i c ker s or t he TV ( or ot her devi ce) does not qui t e come f ul l y up, t hen i t shoul d be saf e t o go t o a l ar ger bul b. 6. 8)
Get t i ng i nsi de a TV
You wi l l voi d t he war r ant y - at l east i n pr i nci pl e. Ther e ar e usual l y no war r ant y seal s on a TV so unl ess you cause vi si bl e damage or mangl e t he scr ews, i t i s unl i kel y t hat t hi s woul d be det ect ed. You need t o deci de. A TV st i l l under war r ant y shoul d pr obabl y be r et ur ned f or warr ant y ser vi ce f or any cover ed pr obl ems except t hose wi t h t he most obvi ous and easy sol ut i ons. Anot her advant age of usi ng warr ant y ser vi ce i s t hat shoul d your pr obl em act ual l y be cover ed by a desi gn change, t hi s wi l l be per f or med f r ee of charge. And, you cannot gener al l y f i x a pr obl em whi ch i s due t o poor desi gn! Get t i ng i nt o a TV i s usual l y qui t e si mpl e r equi r i ng t he r emoval of anywhere f r om 4 t o 16 Phi l i ps or 1/ 4 hex head scr ews - most around t he r ear edge of t he cabi net or under neat h, a coupl e per haps i n t he mi ddl e. Di sconnect t he ant enna and/ or ant enna or cabl e wi r i ng f i r st as i t may st ay wi t h cat ch on t he rear cover you ar e det achi ng. Reconnect what ever i s needed f or t est i ng af t er t he cover i s r emoved. As you pul l t he cover st r ai ght back ( usual l y) and of f , make sur e t hat no ot her wi r es ar e st i l l at t ached. Of t en, t he mai n ci r cui t boar d r est s on t he bott om of t he cover i n some sl ots. Go sl ow as t hi s ci r cui t boar d may t r y t o come al ong wi t h t he back. Once t he back i s of f , you may need t o pr op t he ci r cui t boar d up wi t h a bl ock of wood t o pr event st r ess damage and cont act wi t h t he work surf ace. Most TVs can st i l l be posi t i oned st abl y on any of t hr ee si des ( l ef t , r i ght ,
bot t om) even wi t hout t he r ear cover . However , some r equi r e t he cover f or mechani cal st r engt h or t o not easi l y f al l over . Be car ef ul - l ar ger TVs, i n par t i cul ar, ar e qui t e heavy and bul ky. Get s omeone t o hel p and t ake pr ecaut i ons i f your s i s one of t he unst abl e var i et y. I f need be, t he set can usual l y saf el y be posi t i oned on t he CRT f ace i f i t i s suppor t ed by f oam or a f ol ded bl anket . Reassembl e i n r ever se or der . Get t i ng t he ci r cui t boar d t o sl i de smoothl y i nt o i t s sl ot s may t ake a coupl e of at t empt s but ot her wi se t her e shoul d be no sur pr i ses. 6. 9)
Dust i ng out t he i nsi de of a TV
The f i r st t hi ng you wi l l not i ce when you r emove t he cover i s how super dust y ever yt hi ng i s. Compl ement s t o t he mai d. You never dr eamed t her e was t hat much dust , di r t , and gr i me, i n t he ent i r e house! Use a sof t br ush ( l i ke a new pai nt br ush) and a vacuum cl eaner t o car ef ul l y r emove t he bui l t up dust . Bl owi ng of f t he dust wi l l l i kel y not hur t t he TV unl ess i t get s r edeposi t ed i nsi de var i ous cont r ol s or swi t ches but wi l l be bad f or your l ungs - and wi l l spr ead i t al l over t he r oom. Don' t t ur n anyt hi ng - many cr i t i cal adj ust ment s masquer ade as scr ews t hat j ust beg t o be t i ght ened. Resi st t he i mpul se f or bei ng neat and t i dy unt i l you know exact l y what you ar e doi ng. Be especi al l y car ef ul ar ound t he component s on t he neck of t he CRT - pi ct ur e t ube - as some of t hese ar e easi l y shi f t ed i n posi t i on and cont r ol t he most dr eaded of adj ust ment s - f or col or pur i t y and conver gence. I n par t i cul ar , t her e wi l l be a ser i es of adj ust abl e r i ng magnet s. I t i s a good i dea t o mark t hei r posi t i on i n any case wi t h some whi t e pai nt , ' whi t e out ' , or a Magi c Mar ker so t hat i f t hey do get moved - or you move t hem del i ber at el y, you wi l l know wher e you st ar t ed. Chapt er 7) 7. 1)
TV Adj ust ment s
User pi ct ur e adj ust ment
For gener al vi ewi ng, subdued l i ght i ng but not t ot al darkness i s probabl y best . However , f or most dr amat i c i mpact , a dar kened envi r onment may be pr ef er r ed. Make t he f ol l owi ng adj ust ment s under t he expect ed vi ewi ng condi t i ons. Tune t o a st r ong channel or pl ay a good qual i t y t ape. Tur n t he br i ght ness, cont r ast , and col or cont r ol s al l t he way down. t he t i nt cont r ol ( NTSC) .
Cent er
I ncrease t he br i ght ness unt i l a r ast er i s j ust vi si bl e i n t he dar kest ( shadow) ar eas of t he pi ct ur e. I ncrease t he cont r ast unt i l t he desi r ed i nt ensi t y of hi ghl i ght s i s obt ai ned. Si nce br i ght ness and cont r ast ar e not al ways i ndependent , go back and f or t h unt i l you get t he best pi ct ur e. I ni t i al l y adj ust t he col or cont r ol f or past el shades r at her t han hi ghl y sat ur at ed col or . Set t he t i nt cont r ol f or best f l esh t ones. Then, i ncrease t he col or cont r ol t o obt ai n t he desi r ed degr ee of col or sat ur at i on.
7. 2)
Focus adj ust ment
On a decent TV, you shoul d be abl e t o make out t he i ndi vi dual scanni ng l i nes. I f t hey ar e f uzzy, especi al l y i n br i ght ar eas, t hen f ocus may need t o be adj ust ed. The f ocus pot i s usual l y l ocat ed on t he f l yback t r ansf or mer or on an auxi l i ar y panel near by. The f ocus wi r e usual l y comes f r om t he f l yback or t he gener al ar ea or f r om a t er mi nal on a vol t age t he mul t i pl i er modul e ( i f us ed) . I t i s us ual l y a wi r e by i t s el f goi ng t o t he l i t t l e boar d on t he neck of t he CRT. Let t he set war m up f or at l east hal f an hour . Di spl ay a good qual i t y si gnal . Tur n t he user col or cont r ol al l t he way down and t he br i ght ness and cont r ast cont r ol s al l t he way up. Thi s wi l l be t he wor st case. Adj ust t he f ocus cont r ol f or best over al l shar pness - you may not be abl e to get i t per f ect ever ywher e - cent er as wel l as cor ner s. I f best f ocus i s at one end of t he f ocus pot ' s r ange and st i l l not good enough, t her e may be a pr obl em i n t he f ocus di vi der , f ocus pot , or some r el at ed component . 7. 3)
Adj ust ment of t he i nt er nal SCREEN and col or cont r ol s
The sc r een shoul d be adj ust ed wi t h a whi t e pat t er n ( snow f r om t he t uner shoul d do or t ur n t he user COLOR cont r ol al l t he way down t o get a bl ack and whi t e pi ct ur e) . Put t he set i n Ser vi ce mode ( hor i zont al l i ne) i f i t has such a swi t ch i n t he back or i nsi de. I f not , j ust use t he r ast er i n a darkened r oom. Adj ust scr een f or a di m whi t e l i ne ( r as t e r ) . I f t he l i ne i s not whi t e at i t s di mmes t poi nt , you wi l l need t o adj ust t he dr i ve and cut of f cont r ol s f or R, G, & B. Al t er nat i vel y, you can use t he f ol l owi ng pr ocedur e: ( Fr om LEE) Tur n R, G, and B sc r een ( or backgr ound) cont r ol s down. Now t ur n col or cont r ol f ul l y count er cl ockwi se - - of f . Now t ur n up r ed screen unt i l t he scr een j ust shows a r ed hue. Now t ur n r ed gun down unt i l r ed t i nt j ust goes away. Now do t he same wi t h t he gr een and bl ue scr een cont r ol s. Now adj ust t he t wo DRI VE cont r ol s f or t he best bl ack and whi t e pi ct ur e. That ' s al l t her e i s t o i t . I don' t l i ke t o wor k wi t h j ust a thi n SETUP l i ne. Car t oons seem t o be t he best t hi ng t o have on whi l e doi ng t he above pr ocedur e. You can al so use j ust pl ai n snow ( no pr ogr am) i f you pr ef er . I f you can obt ai n a good B&W pi c. when you' r e done, t he t ube i s good and t he set i f most l i kel y f unct i oni ng pr oper l y. Be pat i ent and go sl ow whi l e wat chi ng t he l ar ge mi r r or t hat you ar e usi ng dur i ng t hi s pr ocedur e. 7. 4)
Col or Bal ance
Col or bal ance needs adj ust ment i f t he hi ghl i ght s and/ or shadows of a bl ack and whi t e pi ct ur e (t ur n t he col or cont r ol al l t he way down) ar e not a per f ectl y neut r al gr ay. To adj ust t he col or bal ance: Tur n t he col or cont r ol al l t he way down so t hat you get what shoul d be a B/ W pi ct ur e. Set t he user br i ght ness and cont r ast cont r ol s about mi d- r ange. The t i nt cont r ol shoul d not mat t er ( i f i t does at t hi s poi nt , you have ot her chr oma pr obl ems or an ' aut ocol or' swi t ch i s on l i mi t i ng t he r ange of some cont r ol s) .
Adj ust t he sub- br i ght ness cont r ol s ( may be cal l ed col or scr een, backgr ound, or t he l i ke) so t hat t he dar k ar eas of t he pi ct ur e ar e j ust vi si bl e and neut r al gr ay. Then, adj ust t he col or gai n cont r ol s unt i l t he br i ght est ar eas ar e neut r al whi t e but not so br i ght t hat t her e i s ' col or bl eedi ng' i n t he hi ghl i ght s . Thi s shoul d get you cl ose. I f somet hi ng i s st i l l shi f t i ng af t er war mup and get some col d- spray or even a l i t t l e bl ower and t r y t o l ocat e t he component t hat i s dr i f t i ng. Mos t l i kel y a t r ans i s t or or c apaci t or . 7. 5)
Hor i zont al posi t i on, si ze, and l i near i t y adj ust ment
Hor i zont al posi t i on may be set vi a a swi t ch or j umper , a pot, or ( most l y i n B/ W TVs) a set of r i ngs on t he CRT neck. Hor i zont al si ze shoul d be set so t hat t her e i s about 10- 15 per cent over scan l ef t and r i ght . Thi s wi l l al l ow ampl e mar gi n f or power l i ne vol t age f l uct uat i ons, component agi ng, and t he r educt i on i n r ast er si ze t hat may occur wi t h some VCR speci al ef f ect s ( f ast pl ay) modes. Many set s no l onger have any hor i zont al si ze adj ust ment s and depend on accur ate r egul at i on of t he vol t age t o t he hor i zont al out put st age t o cont r ol hori zont al si ze. Ther e may be a B+ adj ust ment t o per f orm first. On t hose t hat do, t he adj ust ment may ei t her be done by set t i ng t he B+ vol t age, by a pot , or a wi dt h coi l i n ser i es wi t h t he hor i zont al def l ec t i on coi l s . Moder n set s do not gener al l y have any l i neari t y cont r ol but you may f i nd t hi s on ol der model s. You wi l l need t o go back and f or t h bet ween si ze and l i neari t y as t hese adj ust ment s are usual l y not i ndependent . Some of t he newest set s cont r ol al l t hese par amet er s vi a set t i ngs i n non- vol at i l e memor y and use ser vi ce menus accessed vi a t he r emot e cont r ol f or near l y al l set up adj ust ment s. 7. 6)
Ver t i cal posi t i on, si ze, and l i near i t y adj ust ment
Ver t i cal posi t i on may be set vi a a swi t ch or j umper , a pot , or ( most l y i n B/ W TVs) a set of r i ngs on t he CRT neck. Ver t i cal si ze shoul d be set so t hat t her e i s about 10- 15 per cent over scan t op and bot t om. Thi s wi l l al l ow ampl e margi n f or power l i ne vol t age f l uct uat i ons, component agi ng, and t he r educt i on i n r ast er si ze t hat may occur wi t h some VCR speci al ef f ect s ( f ast pl ay) modes. Some set s no l onger have any ver t i cal si ze adj ust ment s and depend on t he accur at e r egul at i on of t he vol t age t o t he ver t i cal out put st age t o cont r o l ver t i cal s i z e. On t hose t hat do, t he adj ust ment i s usual l y a pot i n t he ver t i cal out put c i r c ui t r y. I f your s et has a l i near i t y c ont r ol , you wi l l need t o adj us t t hi s i n conj unct i on wi t h t he si ze cont r ol as t hese ar e usual l y not i ndependent . Some of t he newest set s cont r ol al l t hese par amet er s vi a set t i ngs i n non- vol at i l e memor y and use ser vi ce menus accessed vi a t he r emot e cont r ol f or near l y al l s et up.
7. 7)
Pi ncushi on adj ust ment s
Ther e may be t wo cont r ol s - ampl i t ude and phase. Pi ncushi on ampl i t ude as i t s name i mpl i es, cont r ol s t he si ze of t he cor r ect i on. Pi ncushi on phase af f ect s wher e on t he si des i t i s appl i ed. Don' t expect per f ect i on. I f t he cont r ol s have no ef f ect , t her e i s pr obabl y a f aul t i n t he pi ncushi on c or r ec t i on ci r c ui t r y . I t i s best t o make t hese adj ust ment s wi t h a cr osshat ch or dot t est pat t er n 7. 8)
Geomet r y adj ust ment
Thi s r ef er s t o i mper f ect i ons i n t he shape of t he pi ct ur e not handl ed by t he pi ncushi on and si ze adj ust ment s. These t ypes of def ect s i ncl ude t r apezoi dal or keyst one shaped rast er and j ogs or wi ggl es ar ound t he per i pher y of t he r ast er . Unf ort unatel y, one way t hese ar e handl ed at t he f act ory i s t o gl ue l i t t l e magnet s t o st r at egi c l ocat i ons on t he CRT and/ or r ot at e l i t t l e magnet s mount ed on t he yoke f r ame. Unl ess you r eal l y cannot l i ve wi t h t he way i t i s ( assumi ng t her e i sn' t somet hi ng act ual l y br oken) , l eave t hese al one! You can end up wi t h wor se pr obl ems. I n any case, car ef ul l y mar k t he posi t i on AND ori ent at i on of ever y magnet so t hat i f t hi s happens, you can get back t o wher e you st ar t ed. I f t he magnet s ar e on l i t t l e swi vel s, some exper i ment i ng wi t h t hem one at a t i me may r esul t i n some i mpr ovement . Of cour se, i t i s best t o obt ai n a ser vi ce manual and f ol l ow i t s i nst r uct i ons. 7. 9)
Why i s t he conver gence on my set bad near t he edges
Ver y si mpl e - nothi ng i s qui t e per f ect . Per f ect conver gence i s not even necessari l y possi bl e i n t heor y wi t h t he set of adj ust ment s avai l abl e on a t ypi cal TV. I t i s al l a mat t er of compr omi ses. Consi der what you ar e t r yi ng t o do: get t hr ee el ect r on beams whi ch or i gi nat e f r om di f f er ent el ect r on guns t o meet at a si ngl e poi nt wi t hi n a f r act i on of a mm ever ywher e on t he scr een. Thi s whi l e t he beams ar e scanni ng at an ef f ect i ve wr i t i ng r at e of 20, 000 mph acr oss t he f ace of a 27 CRT i n a var i abl e magnet i c envi r onment manuf act ur ed at a pr i ce you can af f or d wi t hout a second mor t gage! 7. 10)
CRT pur i t y and conver gence pr obl em
Pur i t y assur es t hat each of t he beams f or t he 3 pr i mar y col ors r ed, gr een, and bl ue - st r i kes onl y t he pr oper phosphor dot s f or t hat col or . A t ot al l y r ed scene wi l l appear pur e r ed and so f ort h. Sympt oms of poor pur i t y ar e bl ot ches of di scol orat i on on t he scr een. Obj ect s wi l l change shades of col or when t he move f r om one par t of t he scr een t o anot her . Conver gence r ef er s t o the cont r ol of t he i nst ant aneous posi t i ons of t he red, gr een, and bl ue spot s as t hey scan across t he f ace of t he CRT so t hat t hey ar e as near l y coi nci dent as possi bl e. Sympt oms of poor conver gence ar e col ored bor der s on sol i d obj ect s or vi si bl e separat e R, G, and B i mages of f i ne l i nes or i mages, NOTE: I t i s best t o f ace the set Nort h- Sout h ( f r ont - t o- back) when doi ng any pur i t y and conver gence adj ust ment s. Si nce you have no way of knowi ng what ori ent at i on wi l l event ual l y be used, t hi s i s t he best compr omi se as t he ear t h' s magnet i c f i el d wi l l be al i gned f r ont - back. Of cour se, i f you know t he f i nal or i ent at i on of t he TV i n your ent er t ai nment cent er - and
you don' t expect t o be redecor at i ng, use t hat i nst ead. Fi r st , make sur e no sour ces of st r ong magnet i c f i el ds are i n t he vi ci ni t y of t he TV - l oudspeaker s, r ef r i gerat or magnet s, MRI scanner s, et c. A near by l i ght eni ng st r i ke or EMP f r om a nucl ear expl osi on can al so af f ect pur i t y. Cycl e power a coupl e of t i mes t o degauss t he CRT ( 1 mi nut e on, 20 mi nut es of f ) - see t he sect i on: Degaussi ng ( demagnet i zi ng) t he CRT. I f t he bui l t i n degaussi ng ci r cui t s have no ef f ect , use an ext er nal manual degaussi ng coi l . Assumi ng t hi s doesn' t hel p, you wi l l need t o set t he i nt er nal pur i t y and/ or conver gence adj ust ment s on t he CRT. Fi r st , mar k t he posi t i ons of al l adj ust ment s - use whi t e pai nt , ' Whi t e out ' , or a Magi c Mar ker on t he r i ng magnet s on t he neck of t he CRT, t he posi t i on and t i l t of t he def l ect i on yoke, and any ot her cont r ol s t hat you may t ouch del i ber at el y or by acci dent . NOTE: i f your set i s st i l l of t he f or t hese adj ust ment s, don' t even a ser vi ce manual and f ol l ow i t t o t he knobs i s cl ear l y mar ked ( some j ob of t hi s) . 7. 11)
t ype wi t h a dr awer or panel of knobs t hi nk about doi ng anyt hi ng wi t hout t he l et t er unl ess t he f unct i ons of al l manuf act ur er s act ual l y do a pr et t y good
CRT pur i t y adj ust ment
Pur i t y on moder n CRTs i s usual l y set by a combi nat i on of a set of r i ng magnet s j ust behi nd t he def l ect i on yoke on t he neck of t he CRT and t he posi t i on of t he yoke f or e- af t . As al ways, mar k t he st ar t i ng posi t i on of al l t he r i ngs and make sur e you ar e adj ust i ng t he cor r ect set i f r i ngs! Use t he f ol l owi ng pur i t y adj ust ment pr ocedur e as a gener al gui de onl y. Dependi ng on t he par t i cul ar model TV, t he f ol l owi ng pur i t y adj ust ment pr ocedur e may subst i t ut e gr een f or r ed. Thi s depends on t he gun pl acement i n t he CRT. Thi s descri pt i on i s based on t he SAMs Phot of act f or t he RCA CTC111C chass i s whi ch uses a sl ot - mask CRT. The pr ocedur es f or dot - mask and Tr i ni t r on ( aper t ur e gr i l l e) CRTs wi l l var y s l i ght l y. See you ser vi ce manual ! Obt ai n a whi t e r ast er ( somet i mes t her e i s a t est poi nt t hat can be gr ounded t o f or ce t hi s) . Then, t ur n down t he bi as cont r ol s f or bl ue and gr een so t hat you have a pur e r ed r ast er. Let t he set war m up f or a mi ni mum of 15 mi nut es. Loosen t he def l ect i on yoke cl amp and move t he yoke as f ar back as i t wi l l go, Adj ust t he pur i t y magnet s t o cent er t he red ver t i cal r ast er on t he scr een. Move t he yoke f or war d unt i l you have t he best overal l r ed pur i t y. Now, move t he yoke f orwar d unt i l you have t he best overal l r ed pur i t y. Ti ght en t he cl amp secur el y and r ei nst al l t he r ubber wedges ( i f you set has t hese) t o st abi l i ze t he yoke posi t i on. Reset t he vi deo adj ust ment s you t ouched t o get a r ed r ast er. 7. 12)
CRT conver gence adj ust ment
I n t he good ol d days when TVs wer e TVs ( and not j ust a pi ct ur e t ube wi t h
a l i t t l e c i r c ui ui t boar d at t ac he hed) t her e wer e l i t er al l y dr dr awer s f ul l of knob knobs s f or set t i ng conve converr gen gence. One coul coul d spen spend hou hour s an and st i l l end end up wi t h a l ess t han sat sat i sf act or y pi ct ur e. As t he t echn chnol ogy pr ogr essed ssed, t he nu number of el ect r oni oni c adj adj ust ment s we went down dr dr ast i cal l y so t hat t oday oday t her e ar e ver ver y f ew i f any. Unl ess you you want ant a l ot of f r ust r at i on, on, I woul oul d r ecom ecommend end not messi ng wi t h conve converr gence. ence. You You coul coul d end end up a l ot wor wor se. I have ave no i dea what i s used used f or conve converr gence gence on your your set but but conve converr gence gence adj adj ust ment ent s ar e nev never er qui qui t e i ndepen epend dent ent of one one anot anot her her . You You coul coul d f i nd an adj adj ust ment ent t hat f i xes xes t he pr pr obl obl em you you t hi nk you you hav have e on onl y t o di di scove scover some ot ot her area of t he screen screen i s t ot al l y screwed. I n addi t i on, t her e ar e adj ust ment s f or geom geomet r y and and pur pur i t y and and maybe aybe ot her her s t hat hat you may acci dent dent al l y move wi t hout out even ven kn knowi ng i t unt i l you you hav have e bu but t one oned up up t he set set . WARNI NG: Accur at el y mar k t he or or i gi nal nal posi t i ons ons - somet i mes you you wi l l chan chang ge somet hi ng t hat wi l l not have an obvi ous ef f ect but wi l l be no not i cea ceabl e l at er on. on. So i t i s ext ext r emel y i mpor t ant ant t o be abl abl e t o get back ack t o where you s t a r t ed. I f onl y r ed/ gr een ver t i c al al l i nes ar e of f s et et , t hen i t i s l i kel kel y t hat onl y a si ngl e ri ng needs t o be be move oved - and by j ust a ha hai r . But , you may acci dent dent al l y move somet hi ng el se! I f you you r eal l y cann cannot l i ve wi t h i t , make ake sur sur e you you mark eve ever yt hi ng ver ver y car car ef ul l y so you you can can get back t o you yourr cur cur r ent st ate. A ser ser vi ce manual i s esse essen nt i al ! Conver ver gence i s set set usi ng a whi t e cr osshatch sshatch or dot dot t est pat t er n. I f you you do not have ave a t est pat t er n gener at or , any any st at i c scen scene ( f r om a camcor cor der or pr evi ousl y r ecor cor ded t ape, f or exam xampl e) wi t h a l ot of f i ne det ai l wi l l suf f i ce. ce. Tur Tur n t he col or cont cont r ol al l t he way down so you you have ave a B/ W pi c t ur e. St at i c conve converr gence set set s t he bea beam ms t o be be coi coi nci dent i n t he exa exact ct cen cent er of t he scr een. Thi Thi s i s don done e usi ng a set of r i ng magn agnet s be behi nd t he pur i t y magnet agnet s on t he CR CRT neck. Fr om t he SAM SAMs f or t he RCA CTC11 TC111C 1C:: adj adj ust t he cent cent er set of magne agnett s t o conve converr ge bl ue t o gr een een at t he cen cent er of t he scr een. en. Adj ust t he r ear set of magn agnet s t o conve converr ge r ed t o gr een een at t he cent cent er of t he scr een een. Your Your set set may have a sl i ght l y di di f f er ent pr oced cedur e. Dynam ynami c conve converr gence ence ad adj ust s f or coi nci dence ence at at t he edge edges s and and cor cor ner s. On ol d t ube, hybr ybr i d, and and ear ear l y sol i d st at e TVs, TVs, dyn dynami c conve converr gence ence was accompl i shed wi t h el ect r oni oni c adj adj ust ment ent s of whi ch t her her e may have have been been a dozen dozen or mor e t hat hat wer e not not i ndep ndepen ende dent nt . Wi t h moder oder n set s, al l conve converr gence gence i s done done wi t h magne agnett r i ngs ngs on t he neck neck of t he CRT, magne agnett s gl ued ued t o t he CRT, and and by t i l t i ng t he def l ect i on yoke yoke.. The cl amp i n con conj unct i on wi t h r ubber wedges or set scr ews assures t hat t he yok yoke e r emai ns i n posi posi t i on. on. Fr om t he SAM SAMs f or t he RCA CTC11 TC111C 1C:: Loosen t he scr ews at t he 6 o' o' cl ock and and 10 o' cl ock posi t i ons t o per mi t t he yoke t o be t i l t ed ver ver t i cal cal l y. Rock yoke up and and down t o conve converr ge t he r i ght and and l ef t si des of t he scr een. Ti ght en scr ew at 6 o' cl ock an and l oosen osen scr ew at 3 o' cl ock ock t o pe per mi t t he yoke yoke t o be be t i l t ed hor i zont zont al l y. Rock yoke yoke f r om si de t o si de t o con conver ver ge t he t op and and bott om of t he scr een. Ti ght en scr ews at at 3 o' cl ock and and 10 o' cl ock. ck. Many any set s s i mpl y use use t he mai n cl amp whi ch l ocks t he yoke t o t he neck neck of t he
CRT i n conj conj unct unct i on wi t h r ubbe ubberr wedge edges s bet bet ween een t he yoke yoke and and t he f unne unnell of t he CRT t o st abi l i ze t he yoke posi t i on posi t i on. Ref er t o you your ser vi ce manual .
( I s t hi s be begi nni ng t o soun sound r epet i t i ous?
For add addi t i onal onal comment ent s on conve converr gence ence ad adj ust ment ent s, see t he sect sect i ons: ons: Tony Tony'' s not not es on set t i ng conve converr gence gence on on del del t a gun gun CR CRTs and Sag Saga a and and Gen Gener er al set up f or l arge CRT TV TVs. 7. 13)
Ti l t ed pi ctur ctur e
You have j ust not i ced t hat t he pi ct ur e on your f ancy ( or cheap) TV i s not qui qui t e hor i zon zont al - not al i gned wi t h t he f r ont beze bezell . Not e t hat of t en t her e i s some k ke eyst oni oni ng as as we wel l wher e t he t op and and bot t om or l ef t and and r i ght edges of t he pi ct ur e are not not qui t e paral l el - whi ch you you may never ver have not i ced ced unt i l now. Si nce t hi s may not be cor cor r ect abl e, adj ust i ng t i l t may r epr esen sent a com compr omi se at at best bet ween t op/ bott om or l ef t / r i ght al i gnment ent of t he pi ct ur e edg edges. You You may never ever sl eep eep agai agai n know knowi ng t hat you your TV pi ct ur e i s not not per per f ect ! BTW, I can can sympat hi ze wi t h you your unhapp appi ness. Not hi ng i s more an annoyi oyi ng t han a j ust not i ceab ceabll e i mper f ect i on such such as t hi s. Ther e ar e s ever al possi poss i bl e causes f or a t i l t ed pi ct ur e: You j ust became awar e of i t but not hi ng has changed. changed. Don' t di s mi ss t hi s of f hand and. I t i s amazi ng how much we i gnore un unl ess i t i s br br oug ought t o our our at t ent i on. Ar e you you a per f ect i oni st ? Ther Ther e moni oni Too may
i s an ext er nal t i l t cont r ol whi ch may be mi sadj ust ed. Newer Sony Sony t ors have ave t hi s ( don' on' t know know abou aboutt TVs) TVs) - a most wond onderf ul add addi t i on. on. bad about about t he st abi l i zi ng wi r es on Tr i ni t r on CRTs. A di gi t al cont r ol have ave l ost i t s memor y acci acci dent al l y. The The ci r cui cui t r y coul coul d have ave a pr obl obl em.
Ther Ther e i s an i nt er nal t i l t cont r ol t hat i s mi sadj ust ed.
Not common.
The def l ect i on yoke on t he CRT has got t en r ot at ed or was not or i ent ed cor r ect l y at t he t i me of t he set ' s manu anuf act act ur e. Somet i mes, t he en ent i r e yok yoke e i s gl ued i n pl pl ace i n ad addi t i on t o be bei ng cl amped ad addi ng anot anot her com compl i cat cat i on. on. On som some moni oni t or s, you you can can r ot at e t he CR CRT sl i ght l y i nst ead but pr obab obabll y not not on you your TV. TV. I f t he TV was r ecent ecent l y bum bumped ped or or hand handll ed r ough oughll y, t he yoke may have have been been knocke knocked d out out of posi t i on. on. But i n most cases, cases, t he amoun ount of abu abuse r equ equi r ed t o do do t hi s wi t h t he yoke yoke f i r ml y cl amped and and/ or gl ued woul oul d have ave t ot al l y dest r oyed yed t he set set i n t he pr pr ocess. cess. Ther e i s a r i sk ( i n addi addi t i on t o t he r i sk of f r yi ng your s el f on t he var i ous vol vol t ages ages pr pr esen esent i nsi de as op oper at i ng TV) TV) of messi ng up t he conve converr gen gence or pur pur i t y when f i ddl i ng wi t h t he yoke yoke or anyt anyt hi ng ar oun ound i t si nce t he yoke yoke posi t i on on t he neck of t he t ube and i t s t i l t may af f ect pur i t y and conve converr gence gence.. Tape Tape any any r ubbe ubberr wedge edges s unde underr t he yoke yoke secur el y i n pl ace as t hese wi l l mai nt ai n t he pr oper posi t i on and t i l t of t he yoke yoke whi l e you you ar e messi ng wi t h i t . ( Don' t assum ssume t he exi st i ng t ape ape wi l l hol d - t he adhesi ve i s pr pr obabl y dr y and br i t t l e) . Ext Ext er nal nal magn agnet i c f i el ds can somet i mes cause cause a r ot at i on wi t hout out any any ot her obvi obvi ous ous ef f ec t s - have have you you chan changed t he TV TV' s l ocat ocat i on? on?
Chapt hapt er 8) 8. 1)
Low Vol t age age Power Supp Suppll y Pr obl ems
Low vol t age age pow power suppl suppl y f unda undam ment ent al s
TVs TVs r equi equi r e a var i et y of vol t ages ( at var i ous power l evel s) t o f unct unct i on. The f unct i on of t he l ow vol t age power suppl y i s t o t ake t he AC l i ne i nput nput of ei t her her 115 115 VA VAC 60 Hz ( 220 220 VA VAC 50 Hz or ot her her AC pow power i n Eur Eur ope and el sewher her e) and pr oduce oduce some of t hese DC vol vol t ages. ages. I n al l cases, cases, t he power t o the the ho hor i zon zont al out put t r ansi st or of t he hor i zon zont al def l ecti on syst syst em i s ob obt ai ned di r ect l y f r om t he l ow vol vol t age power s uppl y. I n som some case cases, s, a var var i et y of ot her DC vol vol t ages ar ar e der i ved ved di r ect l y f r om t he AC l i ne by r ecti f i cat cat i on, f i l t er i ng, and r egul at i on. I n ot her de desi gns, however , most of t he l ow vol vol t age ages ar e der i ved ved f r om secon secondar y wi ndi ngs on t he f l yback yback ( LOPT) t r ansf or mer of t he hor i zon zont al def l ect i on syst syst em. I n st i l l ot her desi desi gns, t her her e i s a separ separ at e swi t chmode ode pow power supp suppl y t hat pr ovi ovi des des some or or al l of t hese vol vol t ages. ages. The Ther e are al so var var i ous ous ( and and somet i mes con convo voll ut ed) combi nat i ons ons of of any any or or al l of t he abov above e. Ther e wi l l al ways be: A power swi swi t ch, ch, r el ay, ay, or t r i ac t o enabl abl e mai n power . A set set of r ecti f i er s - usua sual l y i n a br i dge con conf i gur at i on - t o t ur n t he AC i nt o DC. Smal l cer cer ami c cap capaci t ors ar e normal l y pl pl aced aced acr acr oss t he di ode odes t o r educe RF RF i nt er f er ence. ce. One or mor e l ar ge f i l t er cap capaci t or s t o smoot oot h t he unr egul at ed DC. I n t he U. S. , t hi s i s most of t en a vol vol t age age aroun around 150- 160 V DC. I n coun count r i es wi t h 22 220 VA VAC power, i t wi l l t ypi ypi cal cal l y be be ar ar oun ound 30 300- 320 V DC. A di scret e, hybr i d, or I C r egul at or t o pr pr ovi de st abl e DC t o t he hor i zon zont al def l ect i on syst em. Somet i mes f eed eedback f r om a second secondar ar y out out put of t he f l ybac yback k or eve even n t he hi gh vol vol t age age i s used used.. Thi Thi s r egul at or may be ei t her a l i near or swi t chi chi ng t ype. I n som some case cases, s, t her e i s no no r egul at or . Zer o or or more vol vol t age di di vi der s and and/ or r egul at or s t o pr pr oduce ad addi t i onal vol t ages di di r ectl y f r om t he l i ne power . Thi s r el at i vel y r ar e excep cept f or st ar t up ci r cui cui t s. These vol t ages wi l l not be be i sol sol at ed f r om t he l i ne. A degauss con cont r ol ci r cui cui t usua sual l y i ncl udi ng a t her mi st or or Posi st or ( a com combi nat i on of a heat eat er di sk an and Posi Posi t i ve Tem Temper at ur e Coef oef f i ci ent ent ( PTC PTC) t her mi st or i n a si ngl e pa packag ckage) . When po power i s t ur ned on on, a r el at i vel vel y hi gh AC cur cur r ent ent i s appl appl i ed t o t he degau egauss ss coi l wr app apped ar oun ound t he per i pher y of t he CRT. The The PTC PTC t her mi st er heat s up up, i ncr eases ases i n r esi st ance ance,, and and smoot oot hl y de decr eases ases t he cur cur r ent t o ne near l y zer zer o ove overr a cou coupl e of of secon seconds. A st ar t up ci r cui cui t f or boot i ng t he hor i zon zont al def l ecti on i f var i ous vo vol t ages t o r un t he TV are de der i ved ved f r om t he f l ybac yback. k. Thi Thi s may be an I C or di di scr et e mul t i vi br at or or som somet hi ng el se r unni ng of f a non- i sol sol at ed vol vol t age or t he st and andby pow power suppl suppl y. A st and andby power sup suppl y f or t he mi cr ocon ocontt r ol l er and and r emot e sensor sensor . Usual sual l y, t hi s i s a separat separat e l ow vol vol t age age pow power sup suppl y usi usi ng a smal l power t r ansf ansf ormer f or l i ne i s ol at i on. Al ways ays use an i sol at i on t r ansf ansf or mer wh when wor ki ng on a TV TV but t hi s i s espe speci al l y i mpor t ant - f or you your saf saf et y - when deal i ng wi t h t he non- i sol at ed
l i ne oper at ed power suppl y sect i on. Read and f ol l ow t he saf et y gui del i nes. 8. 2)
Power but t on on set i s f l akey
I f t he on/ of f ( or ot her but t on) on t he set i t sel f behaves er r at i cal l y but t he r emot e cont r ol works f i ne, t hen i t coul d be a di r t y but t on or cabl e or ot her connect i ons t o t he swi t ch PCB, par t i cul ar l y i f t he but t ons on t he set i t sel f ar e r ar el y used. Ther e coul d possi bl y be a bad pul l up r esi st or or somet hi ng of t hat sor t - but i s i t wor t h t he ef f or t t o l ocat e? Why not j ust cont i nue t o use t he r emot e? Ther e i s no r eason t o suspect t hat i t wi l l devel op si mi l ar s ympt oms. However , t her e i s some r i sk t hat i f t he but t on i s di r t y, you may f i nd t he TV comi ng on at r andom t i mes i n t he mi ddl e of t he ni ght ( of cour se! ) . I t hi nk I have an ol der Syl vani a t hat does t hat sor t of t hi ng - don' t r eal l y know as I never use t he power but t on on t he set ! I f power i s cont r ol l ed by a hard swi t ch - a pul l or cl i ck knob, or mechani cal push- push swi t ch and t hi s has become er r at i c due t o wor n cont act s, r epl acement s ar e avai l abl e but of t en onl y di r ect l y f r om t he or i gi nal manuf act ur er t o physi cal l y f i t and ( wher e appl i cabl e) have t he vol ume or ot her cont r ol s bui l t i n. As an al t er nat i ve, consi der mount i ng a smal l t oggl e swi t ch on t he si de of t he cabi net t o subst i t ut e f or t he br oken swi t ch. Thi s wi l l al most cer t ai nl y be easi er and cheaper - and qui t e possi bl y, mor e r el i abl e. 8. 3)
TV bl ows f use
I f t he f use r eal l y bl ows absol ut el y i nst ant l y wi t h no i ndi cat i on t hat t he ci r cui t s ar e f uncti oni ng ( no hi gh pi t ched hor i zont al def l ecti on whi ne (i f your dog hi des under t he couch whenever t he TV i s t ur ned on, def l ect i on i s pr obabl y worki ng) ) , t hen t hi s poi nt s t o a shor t somewher e qui t e near t he AC power i nput . The most common pl aces woul d be: Degauss Posi st or - ver y l i kel y. Hor i zont al out put t r ansi st or . Power suppl y regul at or i f t her e i s one. Power suppl y chopper ( swi t chmode) t r ansi st or i f t her e i s one. Di ode( s) i n mai n br i dge Mai n f i l t er capaci t or ( s ) . You shoul d be abl e t o el i mi nat e t hese one by one. Unpl ug t he degauss coi l as t hi s wi l l show up as a l ow r esi st ance. Fi r st , measur e across t he i nput t o the mai n power r ect i f i er s - i t shoul d not be t hat l ow. A r eadi ng of onl y a f ew ohms may mean a shor t ed r ecti f i er or t wo or a shor t ed Posi st or . Test t he r ect i f i er s i ndi vi dual l y or r emove and r et est t he r esi st ance. Some set s use a Posi st or f or degauss cont r ol . Thi s i s a l i t t l e cubi cal ( about 1/ 2 x 3/ 4 x 1) component wi t h 3 l egs. I t i ncl udes a l i ne oper at ed heat er di sk ( whi ch of t en shor t s out ) and a PTC t her mi st er t o cont r ol cur r ent t o t he degauss coi l . Remove t he posi st or and t r y power . I f t he moni t or now wor ks, obt ai n a r epl acement but i n t he meant i me you j ust won' t have t he aut omat i c degauss.
I f t hese t est good, use an ohmmet er wi t h t he set unpl ugged t o measur e t he hori zont al out put t r ansi st or . Even bet t er t o r emove i t and measur e i t . C- E shoul d be hi gh i n at l east one di r ect i on. B- E may be hi gh or ar ound 50 ohms but shoul d not be near 0. I f any readi ngs ar e under 5 ohms, t he t r ansi st or i s bad. The part s sour ces l i st ed at t he end of t hi s document wi l l have sui t abl e repl acement s. I f t he HOT tests bad, t r y power i ng t he set f i r st wi t h your l i ght bul b and i f i t j ust f l ashes once when t he capaci t or i s char gi ng, t hen put a f use i n and t r y i t . The f use shoul d not bl ow wi t h t he t r ansi st or r emoved. Of cour se, not much el se wi l l wor k ei t her . I f i t t est s good, power t he set wi t hout t he t r ansi st or and see what happens. I f t he f use does not bl ow, t hen wi t h t he good t r ansi st or ( assumi ng i t i s not f ai l i ng under l oad) , i t woul d mean t hat t her e i s some pr obl em wi t h t he dr i vi ng ci r cui t s possi bl y or wi t h t he f eedback f r om t he vol t ages der i ved f r om t he hor i zont al not r egul at i ng pr oper l y. Look i nsi de t he TV and see i f you can l ocat e any ot her l arge power t r ansi st ors i n met al ( TO3) cans or pl ast i c ( TOP3) cases. Ther e may be a separ at e t r ansi st or t hat does t he l ow vol t age r egul at i on or a separ ate regul at or I C. Some TVs have a swi t chmode power s uppl y t hat r uns of f a di f f er ent t r ansi st or t han t he HOT. Ther e i s a chance t hat one of t hese may be bad. I f i t i s a si mpl e t r ansi st or, t he same ohmmet er check shoul d be per f or med. I f none of t hi s pr oves f r ui t f ul , i t may be t i me t o t r y to l ocat e a schemat i c. A bl own f use i s a ver y common t ype of f aul t due t o poor desi gn ver y of t en t r i gger ed by power sur ges due t o out ages or l i ght eni ng st or ms. However , t he most l i kel y par t s to shor t ar e easi l y t est ed, usual l y i n- ci r cui t , wi t h an ohmmet er and t hen easi l y r emoved t o conf i r m. I f you f i nd t he pr obl em and r epai r i t your s el f , t he c os t i s l i kel y t o be under $25. 8. 4)
I nt er nal f use bl ew dur i ng l i ght eni ng st or m ( or el ephant hi t power pol e)
Power sur ges or near by l i ght eni ng st r i kes can dest r oy el ect r oni c equi pment . However , most of t he t i me, damage i s mi ni mal or at l east easi l y r epai r ed. Wi t h a di r ect hi t , you may not r ecogni ze what i s l ef t of i t ! I deal l y, el ect r oni c equi pment shoul d be unpl ugged ( bot h AC l i ne and phone l i ne! ) dur i ng el ect r i cal s t orms i f possi bl e. Moder n TVs, VCRs, mi cr owave ovens, and even st er eo equi pment i s par t i cul arl y suscept i bl e t o l i ght eni ng and sur ge damage because some par t s of t he ci r cui t r y ar e al ways al i ve and t her ef or e have a connect i on t o t he AC l i ne. Tel ephones, modems, and f axes ar e di r ect l y connect ed t o t he phone l i nes. Bet t er desi gns i ncl ude f i l t er i ng and sur ge suppr essi on component s bui l t i n. Wi t h a near - mi ss, t he onl y t hi ng t hat may happen i s f or t he i nt er nal f use t o bl ow or f or t he mi cr ocont r ol l er t o go bonker s and j ust r equi r e power cycl i ng. Ther e i s no possi bl e pr ot ect i on agai nst a di r ect st r i ke. However , devi ces wi t h power swi t ches t hat t ot al l y br eak t he l i ne connect i on ar e mor e r obust si nce i t t akes much mor e vol t age t o j ump t he gap i n t he swi t ch t han t o f r y el ect r oni c par t s. Moni t or s and
TVs may al so have t hei r CRTs magnet i zed due t o t he el ect r omagnet i c f i el ds associ at ed wi t h a l i ght eni ng st r i ke - si mi l ar but on a smal l er scal e t o t he EMP of a nucl ear det onat i on. Was t he TV oper at i ng or on st andby at t he t i me? I f i t was swi t ched of f usi ng an act ual power swi t ch ( not a l ogi c pushbut t on or t he r emot e cont r ol ) , t hen ei t her a component i n f r ont of t he swi t ch has bl own, t he sur ge was enough t o j ump t he gap bet ween t he swi t ch cont act s, or i t was j ust a coi nci dence ( yeh, r i ght ) . I f t he TV was oper at i ng or on st andby or has no act ual power swi t ch, t hen a number of part s coul d be f r i ed. TVs usual l y have t hei r own i nt er nal sur ge pr ot ect i on devi ces l i ke MOVs ( Met al Oxi de Var i st or s) af t er t he f use. So i t i s possi bl e t hat al l t hat i s wr ong i s t hat t he l i ne f use has bl own. Remove t he cover ( unpl ug i t f i r st ! ) and st ar t at t he l i ne cor d. I f you f i nd a bl own f use, r emove i t and measur e across t he i n- boar d si de of f use hol der and t he ot her ( shoul d be t he neut r al ) si de of t he l i ne. The ohmmet er r eadi ng shoul d be f ai r l y hi gh - wel l cer t ai nl y not l ess t han 100 ohms - i n at l east one di r ect i on. You may need t o unpl ug t he degaussi ng coi l t o get a r easonabl e r eadi ng as i t s r esi st ance may be 25 or 30 ohms. I f t he r eadi ng i s r eal l y l ow, t her e ar e ot her pr obl ems. I f t he r esi st ance checks out , r epl ace t he f use and t r y power i ng t he TV. There wi l l be 3 pos si bi l i t i es : I t wi l l wor k f i ne, pr obl em s ol ved. I t wi l l i mmedi atel y bl ow t he f use. Thi s means t her e i s at l east one component shor t ed - possi bi l i t i es i ncl ude an MOV, l i ne rect i f i er s, mai n f i l t er c ap, r egul at or t r ans i s t o r , hor i z ont al out put t r ans i s t o r , et c . You wi l l need t o check wi t h your ohmmet er f or s hor t ed semi conduct or s. Remove any t hat ar e suspect and see of t he f use now sur vi ves ( use t he ser i es l i ght bul b t o cut your l osses - see t he sect i on: The ser i es l i ght bul b t r i ck. I t wi l l not wor k pr oper l y or appear dead. Thi s coul d mean t her e are open f usabl e resi st or s ot her def ect i ve par t s i n t he power suppl y or el sewher e. I n t hi s case f ur t her t est i ng wi l l be r equi r ed and at some poi nt you may need t he schemat i c. I f t he r eadi ng i s ver y l ow or t he f use bl ows agai n, see t he sect i on: TV bl ows f use. 8. 5)
Fuse r epl aced but TV cl i cks wi t h power - on but no ot her act i on
The cl i ck pr obabl y means t hat t he power r el ay i s wor ki ng, t hough t her e coul d be bad cont act s. Si nce t he f use doesn' t bl ow now ( you di d r epl ace i t wi t h one of t he same r at i ngs, r i ght ?) , you need t o check f or : Ot her bl own f uses - occasi onal l y t her e ar e mor e t han one i n a TV. Repl ace wi t h one of exact l y t he same r at i ngs. Open f usabl e r esi st or s. These somet i mes bl ow at t he same t i me or i n pl ace of t he f uses. They ar e usual l y l ow val ues l i ke 2 ohms and ar e i n bi g r ect angul ar cer ami c power r esi st or cases or smal l er bl ue or gr ay
col ored cyl i ndr i cal power r esi st ors. They ar e supposed t o pr otect expensi ve par t s l i ke t he HOT but of t en bl ow at t he same t i me. I f any of t hese ar e bad, t hey wi l l need t o be r epl aced wi t h f l amepr oof r esi st ors of t he same r at i ngs ( t hough you can subst i t ut e an ordi nary r esi st or f or t est i ng pur poses) . Bef or e appl yi ng power , check ( f or shor t s) : Recti f i er di odes Hor i zont al Out put Tr ansi st or ( HOT) Regul at or pass or chopper t r ansi st or ( i f pr esent ) Mai n f i l t er c apac i t or An i ni t i al t est wi t h an ohmmet er can be done whi l e i n- ci r cui t . The r esi st ance acr oss each di ode and t he col l ect or t o emi t t er of t he t r ansi st or s shoul d be r el at i vel y hi gh - a f ew hundr ed ohms at l est i n at l eas t one di r ec t i on ( i n- c i r c ui t ) . I f t her e i s a ques t i on, uns ol der one si de of each di ode and check - shoul d be i n t he Megohms or hi gher i n one di r ect i on. Removed f r om t he ci r cui t , t he col l ect or - emi t t er r esi st ance shoul d be ver y hi gh i n one di r ect i on at l east . Dependi ng on t he t ype, t he base- emi t t er r esi st ance may be hi gh i n one di r ect i on or ar ound 50 ohms. I f any r eadi ng on a semi conduct or devi ce i s under 10 ohms - t hen t he devi ce most l i kel y bad. Assumi ng t hat you do not have a schemat i c, you shoul d be abl e to l ocat e the r ect i f i er s near wher e t he l i ne cor d i s connect ed and t r ace t he ci r cui t . The t r ansi st or s wi l l be ei t her i n a TO3 l ar ge met al can or a TOP3 pl ast i c package - on heat si nks. The f i l t er capaci t or shoul d event ual l y measur e hi gh i n one di r ect i on ( i t wi l l t ake a whi l e t o charge f r om your ohmmet er ) . I t coul d st i l l be f ai l i ng at f ul l vol t age, however . I f you f i nd one bad par t , st i l l check ever ythi ng el se as more t han one part may f ai l and j ust r epl aci ng one may cause i t t o f ai l agai n. Assumi ng ever yt hi ng her e checks out , cl i p a vol t met er set on i t s 500 V scal e or hi gher acr oss t he hor i zont al out put t r ansi st or and t ur n t he power on. War ni ng - never measur e thi s poi nt i f t he hor i zont al def l ect i on i s oper at i ng. i t i s ok now si nce t he set i s dead. I f t he vol t age her e i s 100- 150, t hen t her e i s a pr obl em i n t he dr i ve t o t he hor i z ont al out put c i r c ui t . I f i t i s l ow or 0, t hen t her e are st i l l pr obl ems i n t he power suppl y or wi t h t he wi ndi ng on t he f l yback t r ansf or mer . Ot her possi bl e pr obl ems: Bad hybr i d vol t age r egul at or bad st ar t up ci r cui t Bad r el ay cont act s as ment i oned above. 8. 6)
Power - on t i c k- t i c k- t i c k or c l i c k- c l i c k- c l i c k but no ot her ac t i on
A var i et y of power suppl y or st ar t up pr obl ems can r esul t i n t hi s or s i mi l ar behavi or . Pos si bi l i t i es i nc l ude: Lack of st ar t up hor i zont al dr i ve - see t he sect i on: St art up pr obl ems. The mai n r egul at or i s cycl i ng on over vol t age due t o l ack of l oad. Excessi ve l oad or f aul t y power suppl y cycl i ng on i t s over cur r ent pr o t ect i on ci r cui t . HV shut down, or some ot her syst em det ect i ng an out of r egul at i on condi t i on.
However , i n t hi s case, t her e shoul d be some i ndi cat i on t hat t he def l ect i on and HV i s at t empt i ng t o come up - moment ar y whi ne, st at i c on t he scr een, et c. A dr i ed up mai n f i l t er capaci t or or ot her f i l t er capaci t or i n t he l ow vol t age power suppl y that i s pr oduci ng an out - of - r egul at i on condi t i on unt i l i t war ms up. A bad f i l t er capaci t or on t he out put of a ser i es r egul at or may r esul t i n excessi ve vol t age and subsequent shut down. A pr obl em wi t h t he mi crocont r ol l er , r el ay or i t s dr i ver , or st andby power suppl y. One possi bl e t est woul d be t o var y t he l i ne vol t age and obser ve t he set ' s behavi or . I t may wor k f i ne at one extr eme ( usual l y l ow) or t he ot her . Thi s mi ght gi ve cl ues as t o what i s wr ong. Al so see t he sect i on: Dead TV wi t h per i odi c t weet - t weet - t weet or f l ub- f l ub- f l ub. 8. 7)
No pi ct ur e or r ast er and no sound
The sc r een i s bl ank wi t h no r ast er at al l . Ther e ar e i ndi cat i ons t hat t he channel number s ar e changi ng i n t he di spl ay. Thi s i ndi cat es t hat some of t he l ow vol t ages ar e pr esent but t hese may be der i ved f r om t he st andby suppl y. Assumi ng t her e i s no def l ect i on and no HV, you ei t her have a l ow vol t age power suppl y pr obl em, bad st ar t up ci r cui t , or bad hor i zont al out put t r ansi st or ( HOT) / bad par t s i n t he hor i zont al def l ect i on. Check f or bad f uses. ( I f you have HV as i ndi cat ed by st at i c el ect r i ci t y on t he f r ont of t he scr een and you hear t he hi gh pi t ched whi ne of t he hori zont al def l ect i on when i t i s t ur ned on, t hen t he f ol l owi ng does not appl y). Use an ohmmet er t o t est t he HOT f or short s. I f i t i s bad, l ook f or open f usabl e r esi st or s or ot her f uses you di d not cat ch. Assumi ng i t i s good, measur e t he vol t age on t he col l ect or- emi t t er of t he HOT ( t hi s i s saf e i f t her e i s no def l ect i on) . You shoul d see t he B+ - pr obabl y bet ween 100 and 150 V. I f t her e i s no vol t age, you have a l ow vol t age power suppl y pr obl em and/ or you have not f ound al l t he bad/ open par t s. I f t her e i s vol t age and no def l ect i on ( no hi gh pi t ched whi ne and no HV) , you pr obabl y have a st ar t up pr obl em - al l TVs need some ki nd of c i r c ui t t o ki c k s t a r t t he hor i z ont al def l ec t i on unt i l t he auxi l i ar y power out put s of t he f l yback are avai l abl e. Some Zeni t hs use a si mpl e mul t i vi br at or f or t hi s - a coupl e of t r ansi st or s. Ot her s power t he hor i zont al osc. I C f r om a speci al l i ne- der i ved vol t age. The mul t i vi br at or t ype ar e somet i mes desi gned t o f ai l i f someone keeps t ur ni ng t he set on and of f ( l i ke ki ds pl ayi ng) si nce t he power r at i ng i s i nadequat e. Test t he t r ansi st or s i f i t i s t hat t ype wi t h an ohmmet er . I f one i s shor t ed, you have a pr obl em. The usual way a TV ser vi ce per son woul d t est f or st ar t up pr obl ems i s t o i nj ect a si gnal t o the base of t he HOT of about 15. 75 KHz. I f t he TV t hen st ar t s and r uns once t hi s si gnal i s r emoved, t he di agnosi s i s conf i r med. Thi s i s r i sky - you can bl ow
t hi ngs up i f not car ef ul ( i nc l udi ng your s el f ) . I f you hear t he hi gh pi t ched whi ne of t he def l ect i on t he scree, conf i r m t hat t he hor i zont al def l ect i worki ng by adj ust i ng t he SCREEN cont r ol ( pr obabl y get a rast er t hen your pr obl em i s pr obabl y i n t he ci r cui t s, not t he def l ecti on or hi gh vol t age. 8. 8)
on and/ or f eel some stat i c on and hi gh vol t age ar e on t he f l yback) . I f you can vi deo or chr oma
Reduced wi dt h pi ct ur e and/ or hum bars i n pi ct ur e and/ or hum i n sound
The most l i kel y cause i s a dr i ed up mai n f i l t er capaci t or . Once t he ef f ect i ve capaci t ance dr ops l ow enough, 120 Hz ( or 100 Hz i n count r i es wi t h 50 Hz power ) r i ppl e wi l l make i t s way i nt o t he r egul at ed DC suppl y ( assumi ng f ul l wave r ecti f i cat i on) . Anot her l i kel y cause of si mi l ar sympt oms i s a def ect i ve l ow vol t age r egul ator al l owi ng excessi ve r i ppl e. The r egul at or I C coul d be bad or f i l t er capaci t or f ol l owi ng t he I C coul d be dr i ed up. Ei t her of t hese f aul t s may cause: A pai r of wi ggl es and/ or hum bar s i n t he pi ct ur e whi ch wi l l f l oat up t he scr een. For NTSC wher e t he power l i ne i s 60 Hz but t he f r ame r at e i s 59. 94 Hz, i t wi l l t ake about 8 seconds f or each bar t o pass a gi ven poi nt on t he scr een. ( On some set s, a hal f wave r eci t i f i er i s used r esul t i ng i n a si ngl e wi ggl e or hum bar ) . Hum i n t he sound. t ur ned down.
Thi s may or may not be not i ceabl e wi t h t he vol ume
Possi bl e r egul at i on pr obl ems r esul t i ng i n HV or t ot al shut down or power cycl i ng on and of f . The best appr oach t o t est i ng t he capaci t or s i s t o cl i p a good capaci t or of appr oxi mat el y t he same uF r at i ng and at l east t he same vol t age r at i ng acr oss t he suspect capaci t or ( wi t h t he power of f ) . A capaci t or met er can al so be used but t he capaci t or may need t o be r emoved f r om t he ci r cui t . Once t he capaci t or s have been conf i r med t o be good, vol t age measur ement s on t he r egul at or shoul d be abl e t o nar r ow down t he pr obl em t o a bad I C or ot her component . 8. 9)
TV power cycl i ng on and of f
The power l i ght may be f l ashi ng or i f you ar e r uni ng wi t h a ser i es l i ght bul b i t may be cycl i ng on and of f cont i nuousl y. Ther e may be a chi r pi ng or cl i cki ng sound f r om i nsi de t he set . ( NOTE: usi ng t oo smal l a l i ght bul b f or t he si ze of t he TV may al so r esul t i n t hi s condi t i on. ) I f t her e i s a l ow vol t age r egul at or or separ at e swi t chi ng suppl y, i t coul d be cycl i ng on and of f i f t he hor i zont al out put , f l yback, or one of i t s secondar y l oads wer e def ect i ve. Does t hi s TV have a separ at e l ow vol t age r egul at or and/ or s wi t chi ng power suppl y or i s i t al l par t of t he f l yback ci r cui t ? For t he f ol l owi ng, I assume i t i s al l i n one ( most common) .
Some si mpl e t hi ngs t o t r y f i r st : Ver i f y t hat t he mai n f i l t er capaci t or i s doi ng i t s j ob. Excessi ve r i ppl e on t he rect i f i ed l i ne vol t age bus can cause vari ous f or ms of shut down behavi or. An easy t est i s t o j umper acr oss t he capaci t or wi t h one of at l east equal vol t age r ati ng and si mi l ar capaci t ance ( make connect i ons wi t h power of f ! ) . Use a Var i ac, t he TV wor ks an i ndi cat i on usual l y l at ch 8. 10)
i f possi bl e, t o br i ng up t he i nput vol t age sl owl y and see i f at any poi nt wi t hout shut t i ng down. I f i t does, t hi s coul d be of X- r ay pr ot ecti on ci r cui t ki cki ng i n, t hough t hi s wi l l and keep t he set shut of f i f excessi ve HV wer e det ect ed.
Dead TV wi t h per i odi c t weet - t weet - t weet or f l ub- f l ub- f l ub
A TV whi ch appear s t o be dead except f or a once a second or so t weet or f l ub usual l y i ndi cat es an over l oad f aul t i n t he power suppl y has a shor t i n one of i t s l oad ci r cui t s, ver y of t en a shor t ed r ecti f i er . I t coul d al so be t he f l yback, but check t he t he l oads f i r st . Wai t a f ew mi nut es f or t he f i l t er caps t o di schar ge ( but st ay away f r om t he CRT HV connect or as i t may r et ai n a danger ous and pai nf ul char ge f or a l ong t i me) , use an ohmmet er acr oss t he var i ous di odes i n t he power suppl y. Usi ng an ohmmet er on t he r ect i f i er di odes, t he r esi st ance i n at l east one di r ect i on shoul d be gr eat er t han 100 ohms. I f i t i s much l ess ( l i ke 0 or 5 ohms) , t hen t he di ode i s pr obabl y bad. Unsol der and check agai n - i t shoul d t est i nf i ni t e ( gr eat er t han 1M ohms) i n one di r ecti on. Ot her possi bl e causes: Bad sol der connect i ons. Ot her shor t ed component s l i ke capaci t or s. Ot her pr obl ems i n t he power suppl y. Bad f l yback. Shor t or excessi ve l oad on secondary suppl i es f ed f r om f l yback. Pr obl em wi t h st ar t up dr i ve ( cycl i ng on over vol t age) . 8. 11)
Shor t ed Component s
A f ai l ur e of t he hor i zont al out put t r ansi st or or power suppl y swi t chmode t r ans i s t o r wi l l bl ow a f us e or f us abl e r es i s t o r . Look f or bl own f uses and t est f or open f usabl e r esi st ors i n t he power ci r cui t s. I f you f i nd one, t hen t est t he HOT and/ or swi t chmode t r ansi st or f or shor t s. Ot her pos si bi l i t i es : r ec t i f i er di odes or mai n f i l t er c apac i t or . Whi l e you are at i t , check f or bad connect i ons - pr od the ci r cui t board wi t h an i nsul at ed st i ck when t he pr obl em r eoccur s - as t hese can cause part s t o f ai l . 8. 12)
St ar t up pr obl ems - not hi ng happens, cl i ck, or t i ck- t i ck- t i ck sound
TVs and moni t or s usual l y i ncor por at e some ki nd of st ar t up ci r cui t t o pr ovi de dr i ve t o t he hor i zont al out put t r ansi st or ( HOT) unt i l t he f l yback power suppl y i s r unni ng. Yes, TVs and moni t or s boot j ust l i ke comput er s. Ther e ar e t wo t ypi cal ki nds of sympt oms: power on cl i ck but not hi ng el se
happens or a t i ck- t i ck- t i ck sound i ndi cat i ng cycl i ng of t he l ow vol t age ( l i ne r egul at or ) but l ac k of s t a r t up hor i z ont al dr i ve. Check t he vol t age on t he hor i zont al out put t r ansi st or ( HOT) . I f no vol t age i s present , t her e may be a bl own f use or open f usabl e r esi st or - and pr obabl y a shor t ed HOT. However , i f t he vol t age i s nor mal ( or hi gh) - usual l y 100- 150 V, t hen t her e i s l i kel y a pr obl em wi t h t he s t a r t up c i r c ui t not pr ovi di ng i ni t i al base dr i ve t o t he HOT. The st ar t up ci r cui t s may t ake sever al f or ms: Di scr et e mul t i vi br at or or ot her si mpl e t r ansi st or ci r cui t t o pr ovi de base dr i ve t o t he HOT. I C whi ch i s par t of def l ect i on chai n power ed of f of a vol t age di vi der or t r ansf or mer . Ot her t ype of ci r cui t whi ch oper at es of f of t he l i ne whi ch pr ovi des some ki nd of dr i ve t o t he HOT. The st ar t up ci r cui t may oper at e of f of t he st andby power suppl y or vol t age der i ved f r om non- i sol at ed i nput . Be car ef ul - of cour se, use an i sol at i on t r ansf or mer whenever wor ki ng on TVs and especi al l y f or power suppl y pr obl ems. Not e t hat one common way of ver i f yi ng t hat t hi s i s a st art up pr obl em i s t o i nj ect a 15 KHz si gnal di r ect l y i nt o the HOT base or dr i ver ci r cui t ( j ust f or a second or t wo). I f t he TV t hen st ar t s up and cont i nues t o r un, you know t hat i t i s a st ar t up pr obl em. CAUTI ON: Be car ef ul i f you do t hi s. The HOT ci r cui t may be l i ne- connect ed and i t i s possi bl e t o dest r oy t he HOT and r el at ed component s i f t hi s i s not done pr oper l y. I once managed t o ki l l not onl y t he HOT but t he chopper t r ansi st or as wel l whi l e wor ki ng i n t hi s ar ea. An expensi ve l esson. I have al so seen st ar t up ci r cui t s t hat wer e desi gned t o f ai l . Tur ni ng t he TV on and of f mul t i pl e t i mes woul d exceed t he power r at i ngs of t he component s i n t he st ar t up ci r cui t . Some Zeni t h model s have t hi s ' f eatur e' . When t hi s si t uat i on exi st s, i t coul d be t hat t he ci r cui t i s not pr ovi di ng t he pr oper dr i ve or t hat due t o some ot her ci r cui t condi t i on, t he dr i ve i s not al ways suf f i ci ent t o get t he secondar y suppl i es goi ng t o t he poi nt t hat t he nor mal ci r cui t s t ake over . I woul d st i l l check f or bad connect i ons - pr od t he ci r cui t boar d wi t h an i nsul ated st i ck when the pr obl em r eoccur s 8. 13)
TV t ur ns of f af t er war mi ng up
I f you can t ur n i t back on wi t h t he s moment ar y key or power but t on: When i t shut s of f , do you need t o push t he power but t on once or t wi ce t o get i t back on? Al so, does anyt hi ng el se about t he pi ct ur e or sound change as i t war ms up? I f once, t hen t he cont r ol l er i s shut t i ng t he TV down ei t her as a resul t of
a ( t her mal l y i nduced) f aul t i n t he cont r ol l er or i t sensi ng some ot her pr obl em. Moni t or i ng t he vol t age on t he r el ay coi l ( assumi ng t hese i s one) coul d hel p det er mi ne what i s happeni ng. The cont r ol l er t hi nks i t i s i n char ge. I f t wi ce, t hen t he power suppl y i s shut t i ng down as t he cont r ol l er st i l l t hi nks i t i s on and you ar e r eset t i ng i t . A coupl e of possi bi l i t i es her e woul d be l ow vol t age or hi gh vol t age r egul at i on er r or ( excessi ve hi gh vol t age i s s ensed and causes shut down t o pr event danger ous X- r ay emi ssi on) . A par t i al l y dr i ed up mai n f i l t er capaci t or coul d al so cause a shut down but t her e mi ght be ot her sympt oms l i ke hum bar s i n t he pi ct ur e j ust bef ore t hi s happened. Cl i ppi ng a good capaci t or acr oss t he suspect ( wi t h power of f ! ) woul d c onf i r m or el i mi nat e t hi s pos si bi l i t y. I f i t uses a pul l - knob ( or ot her har d on/ of f swi t ch) , t hen t hi s may be l i ke pul l i ng t he pl ug and woul d r eset any abnormal condi t i on. 8. 14)
TV doesn' t power up i mmedi at el y
The TV may do not hi ng, cycl e on and of f f or a whi l e, power up and t hen shut down i n an endl ess cycl e - or at l east f or a whi l e. Then i t comes on and oper at es nor mal l y unt i l i t i s t ur ned of f . A c oupl e of pos s i bi l i t i es : The mai n f i l t er capaci t or or ot her f i l t er capaci t or s i n t he l ow vol t age power suppl y i s dri ed up and t hi s can cause al l ki nds of r egul at i on pr obl ems. The power suppl y r egul at or i s def ect i ve ( or mar gi nal ) al l owi ng excess i ve vol t age on i t s out put and t hen t he X- r ay pr ot ect i on ci r cui t r y shut s you down. I f you can get access t o a Var i ac, i t woul d be wor t h br i ngi ng up t he i nput vol t age sl owl y and seei ng i f t her e i s some poi nt at whi ch i t woul d st ay on. I f t her e i s, t hen i f t he pi cture has ser i ous hum bar s i n i t t he mai n f i l t er cap coul d be bad. I f mor e or l ess a decent pi ct ur e wi t h mi nor hum bar s t hen i t coul d be the regul at or . 8. 15)
Ol d TV r equi r es war mup per i od
So, what el se i s new? I n t he ol d days, a TV was expect ed t o t ake a f ew mi nut es ( at l east ) t o war m up. We ar e al l spoi l ed t oday. Of cour se, you usual l y mai nt ai ned a f ul l t i me t echni ci an or engi neer t o f i ddl e wi t h t he conver gence adj ust ment s! A TV ( f r om around 1983) needs at l east 5 mi n. t o warm up ( l i ght i ng up t he scr een and maki ng sound i f I gi ve i t a col d st ar t . Once war med up, you can i t of f and on agai n f r om t he f r ont panel and i t wi l l work i mmedi atel y. Anot her t hi ng t hi s TV has a sub- power swi t ch i n t he r ear . 1983 sounds a bi t l at e, but set s i n t he l at e ' 70 dur i ng t he t r ansi t i on f r om t ubes t o al l sol i d st at e chassi s of t en had t he ' sub- power ' swi t ch pr ovi di ng some power t o t he f i l ament s of t he CRT and ot her t ubes - usual l y i n t he def l ect i on and hi gh vol t age ci r cui t s si nce t hese woul d take a whi l e t o heat up and st abi l i ze. The i dea was t o l eave t hi s swi t ch on al l t he t i me ( except when goi ng on vacat i on - i t was somet i mes l abel ed ' vacat i on' ) so t hat you woul d
have near l y i nst ant war m up. Supposedl y, t hi s l ed t o an i ncr eased r i sk of f i r e as wel l ( see t he secti on: About i nst ant on TVs) . I f i t i s a tot al l y sol i d st at e chassi s, t hen t her e i s some component - pr obabl y a capaci t or i n t he power suppl y si nce i t af f ect s bot h pi ct ur e and sound - t hat i s dr i f t i ng wi t h t emper at ur e and needs t o be l ocat ed wi t h col d spray or a heat gun. 8. 16)
Rel ays i n t he Power Ci r cui t r y of TVs
What exact l y i s t he pur pose of such a r el ay . . . i . e. , why doesn' t t he power swi t ch on t he TV j ust appl y power di r ect l y i nst ead of t hr ough a r el ay? The usual r eason f or a r el ay i nst ead of a knob swi t ch i s t o per mi t a r emot e cont r ol t o t ur n power on and of f . I f your TV does not have a r emot e, t hen i t i s si mpl y t he same chassi s mi nus 24 cent s wort h of ci r cui t r y t o do t he r emot e f unct i on. I sn' t mar ket i ng wonder f ul ? The onl y unknown i s t he coi l vol t age. I t i s pr obabl y somewher e i n t he 6- 12 vol t r ange. You shoul d be abl e t o measur e t hi s on t he coi l t er mi nal s i n oper at i on. I t wi l l be a DC coi l . However , t he r el ay cont r ol s t he 125 VAC ( or 220) whi ch you shoul d t r eat wi t h r espect - i t i s a l ot mor e danger ous t han t he 25KV+ on t he CRT! Al most cer t ai nl y, t he rel ay wi l l have 4 connect i ons - 2 f or power and 2 f or t he coi l . I f i t i s not mar ked t hen, i t shoul d be pr et t y easy t o l ocat e t he power connect i on. One end wi l l go t o st uf f near t he AC l i ne and t he ot her end wi l l go t o t he r ect i f i er or maybe a f usabl e r esi st or or somet hi ng l i ke t hat . These wi l l l i kel y be beef i er t han t he coi l connect i ons whi ch wi l l go bet ween a t r ansi st or and GND or some l ow vol t age, or maybe di r ect l y i nt o a bi g mi crocont r ol l er chi p. Of cour se, t he best t hi ng woul d be t o get t he schemat i c. Some bi g publ i c l i br ar i es car r y t he SAMs phot of act ser i es f or TVs and VCRs. I f not , t ake 10 mi nut es and t r ace i t . You shoul d be abl e t o get f ar enough t o det er mi ne t he r el ay connect i ons. Once you ar e sur e of t he AC connect i ons - measur e acr oss t hem whi l e i t i s of f and al so whi l e i t i s on. Whi l e of f , you shoul d get 110- 125 VAC. Whi l e on and wor ki ng - 0. Whi l e on and not wor ki ng ei t her 110- 125 VAC i f t he r el ay i s not pul l i ng i n or 0 i f i t i s and t he pr obl em i s el s ewher e. We can deal wi t h t he l at t er case i f needed l at er on. Not e t he even i f t he r el ay cont act s ar e not wor ki ng, t he pr obl em coul d st i l l be i n t he cont r ol ci r cui t r y not pr ovi di ng t he cor r ect coi l vol t age/ cur r ent , t hough not l i kel y. I t may be expensi ve and/ or di f f i cul t t o obt ai n an exact r epl acement , but t hese ar e pr et t y vani l l a f l avor ed as r el ays go. Any good el ect r oni cs di st r i but or shoul d be abl e to suppl y a sui t abl e el ect r i cal r epl acement t hough you may need t o be cr eat i ve i n mount i ng i t . 8. 17)
Fl amepr oof Resi st ors
Fl amepr oof Resi st or or Fusabl e Resi st or ar e of t en desi gnat ed by t he symbol ' FR' . They ar e t he same.
You may see t hese i n t he swi t chmode power suppl i es used i n TVs and moni t or s. They wi l l l ook l i ke power r esi st or s but wi l l be col or ed bl ue or gr ay, or may be r ect angul ar cer ami c bl ocks. They shoul d onl y be r epl aced wi t h f l amepr oof r esi st or s wi t h i dent i cal r at i ngs. They ser ve a ver y i mpor t ant saf et y f unct i on. These usual l y ser ve as f uses i n addi t i on t o any ot her f uses t hat may be pr esent ( and i n addi t i on t o t hei r f uncti on as a r esi st or , t hough t hi s i sn' t al ways needed) . Si nce your FR has bl own, you pr obabl y have shor t ed semi conduct ors t hat wi l l need t o be r epl aced as wel l . I woul d check al l t he t r ansi st ors and di odes i n t he power suppl y wi t h an ohmmet er . You may f i nd t hat t he mai n swi t ch mode t r ansi st or has deci ded t o t ur n i nt o a bl ob of sol der - dead shor t . Check ever yt hi ng out even i f you f i nd one bad par t - many component s can f ai l or cause ot her component s t o f ai l i f you don' t l ocat e t hem al l . Check r esi st or s as wel l , even i f t hey l ook ok. Then, wi t h a l oad on t he out put of t he power suppl y use a Var i ac t o br i ng up t he vol t age sl owl y and obser ve what happens. At 50 VAC or l ess, t he swi t cher shoul d ki ck i n and pr oduce some out put t hough cor r ect r egul at i on may not occ ur unt i l 80 VAC or mor e. The out put s vol t ages may even be gr eat er t han spec' d wi t h a smal l l oad bef or e regul at i on i s cor r ect . Chapt er 9) 9. 1)
Def l ect i on Pr obl ems
Def l ect i on f undament al s
The el ect r on beams i n t he CRT need t o be sc anned hor i zont al l y and ver t i cal l y i n a ver y pr eci se manner t o pr oduce a rast er - and a pi ct ur e. For NTSC and PAL, t he hor i zont al scan r at es ar e 15, 734 and 15, 625 Hz r es pec t i vel y. For NTSC and PAL, t he ver t i cal scan r at es ar e 60 and 50 Hz ( appr oxi mat el y) r es pec t i vel y. The def l ect i on yoke i ncl udes set s of coi l s f or hor i zont al and ver t i cal scanni ng or i ent ed at 90 degr ees wi t h r espect t o each ot her . Addi t i onal coi l s ar e needed t o cor r ect f or pi ncushi on and ot her geomet r i c def ect s. The def l ect i on ci r cui t s must be synchr oni zed and phase l ocked t o t he i ncomi ng vi deo si gnal . Ther ef or e, we have t he f ol l owi ng f unct i ons: Sync separ at or t o obt ai n hor i zont al and ver t i cal synchr oni zat i on pul ses. Hor i zont al osci l l at or whi ch l ocks t o hor i zont al sync pul ses. Hor i zont al dr i ve f ol l owed by hor i zont al out put whi ch f eeds def l ect i on yoke ( and f l yback f or HV and ot her vol t ages) , Yoke r equi r es a sawt oot h cur r ent wavef or m f or l i near hor i zont al def l ecti on. Hor i zont al out put i n al l but t he smal l er TVs i s a l ar ge di scret e power t r ansi st or , most of t en an NPN bi pol ar t ype. Ver t i cal osci l l at or whi ch l ocks to ver t i cal sync pul ses. sawt oot h wavef or m f or l i near ver t i cal def l ecti on.
Yoke r equi r es
Ver t i cal dr i ve/ out put whi ch f eeds ver t i cal def l ect i on yoke. use I Cs f or ver t i cal dr i ve and out put .
Newer TVs
Var i ous addi t i onal def l ect i on si gnal s t o cor r ect f or t he i mper f ect i ons i n t he geomet r y of l ar ge angl e def l ect i on CRTs. These may be f ed i nt o t he normal def l ect i on coi l s and/ or t her e may be separat e coi l s mount ed on t he neck of t he CRT. 9. 2)
Why ar e near l y al l hor i zont al dr i ver s ci r cui t s tr ansf or mer coupl ed?
One ( pr obabl y secondary) r eason i s t hat t hi s provi des one of t he i sol at i on barr i ers bet ween a l i ne- connect ed HOT and f l yback pr i mary and t he si gnal ci r cui t s of t he TV. A more i mpor t ant r at i onal i s t hat a t r ansf ormer i s ni ce easy way of i mpedance mat chi ng t he hor i zont al dr i ver ci r cui t ( 100s t o 1000s of ohms) t o t he f ew ohm i nput i mpedance of t he hori zont al out put t r ansi st or base whi ch r equi r es upwar ds of several amps f or proper dr i ve. A t ypi cal dr i ver t r ansf ormer may be i n t he 5- 10: 1 t ur ns r at i o r epr esent i ng 25- 100: 1 i mpedance r at i o. A bypr oduct of al l t hi s i s t hat i t i s al most i mpossi bl e f or a f aul t y dr i ver st age t o ki l l t he HOT. 9. 3)
Pi ct ur e squeezed i n t hen di ed
You wer e wat chi ng ' Kni ght Ri der ' r er uns and al l of a sudden, t he pi ct ur e squeezed i n sl owl y f r om t he r i ght hand si de. I t squeezed i n about 2 i nches or so when t he ent i r e pi ct ur e went dead - has r emai ned l i ke t hi s si nce. Sound i s f i ne, but no act i vi t y at al l f r om t he t ube. Has i t di ed? How much t i me, ef f or t , and expense t o f i x? No, i t ' s not dead, at l eas t i t c er t ai nl y i s not t he pi c t ur e t ube. Your set pr obabl y di dn' t l i ke Kni ght Ri der - at l east t hat epi sode! Ser i ousl y, how ol d i s t he set ? I s i t a t ot al l y sol i d st at e chassi s or ar e t her e t ubes i n t he def l ecti on ci r cui t s? I s t her e any i ndi cat i on of l i ght on t he scr een? Any i ndi cat i on of t he 15735 Hz hor i zont al r unni ng at al l ? ( You woul d nor mal l y hear t he hi gh pi t ch sound) . Newer TVs al most al ways der i ve vol t ages f or t he sound ci r cui t s f r om t he hor i zont al def l ect i on but ol der hybr i ds may r un t he sound of f of i t s own power . I n any case, t her e i s a pr obl em i n t he hor i zont al def l ect i on and you pr obabl y have no hi gh vol t age as wel l assumi ng no l i ght on t he scr een. The f act t hat i t squeezed i n f i r st i ndi cat es t hat a par t i al shor t or ot her f aul t may have devel oped i n t he hor i zont al def l ect i on ci r cui t s - possi bl y t he def l ect i on yoke or f l yback t r ansf ormer . I t coul d al so have been a bad connect i on l et t i ng l oose. Once i t f ai l ed compl et el y, t he hor i zont al out put t r ansi st or may have bought t he f arm or bl own a f use. 9. 4)
Hor i zont al def l ect i on shut t i ng down
Conf i r m t hat t he hor i zont al def l ect i on i s shut t i ng down ( al ong wi t h t he hi gh vol t age s i nc e i t i s der i ved f r om hor i z ont al def l ec t i on: l i s t e n f or t he hi gh pi t ched def l ect i on whi ne, t est f or st at i c on t he screen,
see i f t he CRT f i l ament s ar e l i t , t ur n up t he br i ght ness and/ or scr een cont r ol t o see i f you can get a r ast er ) and t hen why: Power i s f ai l i ng t o t he hor i zont al out put t r ansi st or - t hi s coul d be due t o a l ow vol t age power suppl y pr obl em, bad connect i on, et c. Base dr i ve to t he hor i zont al out put t r ansi st or i s f ai l i ng - coul d be a f aul t i n t he hor i zont al osci l l at or or bad connecti on. Pr obl em wi t h t he f l yback t r ansf or mer or i t s secondar y l oads ( f l yback may pr ovi de ot her power vol t ages) . X- r ay pr ot ect i on i s act i vat i ng - ei t her due to excess HV or due to a f aul t i n t he X- r ay pr ot ec t i on c i r c ui t r y. I f t he pr obl em comes and goes er r at i cal l y i t sounds l i ke a bad connect i on, especi al l y i f whacki ng has an ef f ect . I f i t comes and goes per i odi cal l y, t hen a component coul d be heat i ng up and f ai l i ng, t hen cool i ng, et c. 9. 5)
Hor i z ont al l oc k l os t
A TV whi ch l oses hor i zont al l ock when changi ng channel s, moment ar i l y l osi ng t he si gnal , or swi t chi ng i nput s may have a hor i zont al osci l l at or t hat i s way out of adj ust ment or has dr i f t ed i n f r equency due t o agi ng component s. Not e t hat f or t ot al and/ or up pi ctur e wi
t he char acteri st i cs of t hi s ar e di st i nctl y di f f er ent t han l os s of s ync . I n t he l at t er c as e, t he pi c t ur e wi l l dr i f t s i deways and down whi l e wi t h an of f f r equency osci l l at or, t he t orn up l l t r y at l east t o r emai n st at i onar y.
Thi s coul d be a capaci t or or ot her si mi l ar par t . Or , t he osc i l l at or f r equency may j ust need t o be t weaked (par t i cul ar l y wi t h ol der set s) . Ther e may be an i nt er nal hor i zont al f r equency adj ust ment - ei t her a pot or a coi l - whi ch may need a sl i ght t weak. I f a coi l , use a pl ast i c al i gnment t ool , not met al t o avoi d cracki ng t he f r agi l e cor e. A schemat i c wi l l be usef ul t o l ocat e t he adj ust ment i f any or t o i dent i f y possi bl e def ect i ve par t s. Tr y a l ar ge publ i c l i br ar y f or t he SAMs Phot of act f or t hi s s et . 9. 6)
Ver t i cal squashed
Thi s i s a ver t i cal def l ect i on pr obl em - possi bl y a bad capaci t or , bad connect i on, or ot her component . None of t hese shoul d be ver y expensi ve ( i n a r el at i ve s or t of way) . St ar t by subst i t ut i ng a good capaci t or f or each el ect r ol yt i c i n t he ver t i cal out put ci r cui t . Look f or bad connecti ons (par t i cul ar l y t o t he def l ect i on yoke) , t hen consi der r epl aci ng t he ver t i cal out put I C or t r ans i s t or ( s ) . The f ol l owi ng ar e NOT possi bl e: CRT, f l yback, t uner . ( I am j ust t r yi ng t o t hi nk of r eal l y expensi ve par t s t hat cannot possi bl y be at f aul t ) . Not e t hat s ome movi es or l aser kar aoke di scs are r ecor ded i n ' l et t er box' f or mat whi ch at f i r st gl ance l ooks l i ke a squashed ver t i cal pr obl em. However , t he pi ct ur e aspect r at i o wi l l be cor r ect and t ur ni ng up t he br i ght ness wi l l
r eveal a perf ect l y normal r ast er above and bel ow t he pi ct ur e. 9. 7)
Par t of pi c t ur e c ut of f
The f ol l owi ng appl i es i f t he par t of t he pi ct ur e i s mi ss i ng but not ot her wi se squashed or di st ort ed. For exampl e, 85% i s mi ssi ng but t he por t i on s t i l l vi s i bl e i s nor mal s i z e. Wow! That ' s an i nt er est i ng one, mor e so t han t he typi cal r un- of - t he- mi l l my TV j ust up and di ed on me. Or , my pet or angut an j ust put a hol e i n t he CRT, what shoul d I do? Si nce t he si ze of t he pi ct ur e f r agment i s cor r ect but 85% i s mi ssi ng, my f i r st t hought woul d be t o check wavef orms goi ng i nt o t he ver t i cal out put st age. The suppl y vol t age i s pr obabl y cor r ect si nce t hat of t en det er mi nes t he si ze. I t al most sounds l i ke t he wavef orm r ather t han bei ng most l y on ( act i ve vi deo) and of f f or t he shor t bl anki ng per i od i s somehow onl y on dur i ng t he l ast part of t he act i ve vi deo t hus gi vi ng you j ust t he bot t om of t he pi cture. I f t her e i s a ver t i cal out put I C, i t may be def ect i ve or t he bl anki ng i nput t o i t may be cor r upt ed. The pr obl em may be as f ar back as t he sync separ at or . Then agai n who knows, maybe wai t f or t he schemat i cs. 9. 8)
Si ngl e Ver t i cal Li ne
Si nce you have hi gh vol t age, t he hori zont al def l ect i on ci r cui t s ar e al most cer t ai nl y wor ki ng ( unl ess t her e i s a separ at e hi gh vol t age power suppl y al most unhear d of i n moder n TVs and ver y uncommon i n al l but t he most expensi ve moni t or s) . Check f or bad sol der connect i ons bet ween t he mai n boar d and t he def l ect i on yoke. Coul d al so be a bad hor i zont al coi l i n t he yoke, l i near i t y coi l , et c. Ther e i s not t hat much t o go bad based on t hese sympt oms ass umi ng t he hi gh vol t age and t he hor i zont al def l ect i on use t he same f l yback. I t i s al most cer t ai nl y not an I C or t r ansi st or t hat i s bad. 9. 9)
Si ngl e Hor i zont al Li ne
A si ngl e hor i zont al l i ne means t hat you have l ost ver t i cal def l ect i on. Hi gh vol t age i s most l i kel y f i ne si nce t her e i s somet hi ng on t he scr een. Thi s coul d be due t o: Di r t y ser vi ce swi t ch cont act s. Ther e i s of t en a smal l swi t ch on t he l ocat ed i nsi de on t he mai n boar d or per haps accessi bl e f r om t he back. Thi s i s used dur i ng set up t o set t he col or backgr ound l evel s. When f l i pped t o t he ' s er vi c e' pos i t i on, i t ki l l s ver t i c al def l ec t i on and vi deo t o t he CRT. I f t he swi t ch somehow changed posi t i on or got di r t y or cor r oded cont act s, you wi l l have t hi s sympt om. Fl i p t he swi t ch back and f or t h a coupl e of t i mes. I f t her e i s some change, t hen r epl ace, cl ean, r esol der , or even bypass i t as appr opr i at e. Bad connect i on t o def l ect i on yoke or ot her par t s i n ver t i cal out put ci r cui t . Bad connect i ons ar e common i n TVs and moni t or s. Check around t he pi ns of l ar ge component s l i ke t r ansf ormers , power t r ansi st or s and r esi st or s, or connect or s f or hai r l i ne cracks i n t he sol der . Reseat i nt er nal connect ors. Check par t i cul ar l y ar ound t he connect or t o the def l ect i on yoke on t he CRT.
Bad ver t i cal def l ect i on I C or t r ansi st or . You wi l l pr obabl y need t he ser vi ce manual f or t hi s and t he f ol l owi ng. However , i f t he ver t i cal def l ect i on i s done wi t h an I C, t he ECG Semi conduct or Mast er Subst i t ut i on gui de may have i t s pi nout whi ch may be enough t o t est i t wi t h a scope. Ot her bad par t s i n ver t i cal def l ect i on ci r cui t t hough t her e ar e not t hat many par t s t hat woul d ki l l t he def l ect i on ent i r el y. Loss of power t o ver t i cal def l ect i on ci r cui t s. f usabl e r esi st or s/ f uses and bad connect i ons.
Check f or bl own
Los s of ver t i cal os ci l l at or or ver t i cal dr i ve s i gnal s . The most l i kel y possi bi l i t i es ar e i n t he def l ect i on out put st age or bad connect i ons t o t he yoke. 9. 10)
Loss of Hor i zont al Sync ( al so appl i es to ver t i cal ) af t er War mup
The pr obl em l i es ei t her i n t he hor i zont al osc i l l at or or i n t he sync syst em. I f i t r eal l y i s a pr obl em wi t h sync pul ses not r eachi ng t he osci l l at or , t he pi ct ur e wi l l move ar ound hori zont al l y and can be br ought t o hol d moment ar i l y wi t h t he hol d cont r ol . I f t he pi ct ur e br eaks up i nt o st r i ps, t her e i s a pr obl em i n t he hor i zont al osci l l at or . Rot at e t he hol d cont r ol : i f t he f r equenc y i s t oo f ar of f , t he pi c t ur e wi l l not s et t l e i nt o pl ac e at any adj ust ment of t he hol d cont r ol . Look around t he hor i zont al osci l l ator c i r c ui t : al l of t he os ci l l at or par t s wi l l be r i ght t her e, or c hec k on t he hor i zont al osci l l at or modul e. Anot her hor i zont al pr obl em can occur i f t he set i s an RCA made f r om ar ound 1972- 1980: t hese set s ar e desi gned t o sl i p ver y f ar of f sync i f t he hi gh vol t age i s t oo hi gh, t o pr ot ect agai nst r adi at i on. Tur ni ng up t he br i ght ness wi l l decr ease t he number of bar s i f t hi s syst em i s i n quest i on, as t he hi gh vol t age i s decreasi ng. I n t hi s case, check ar ound t he hi gh- vol t age r egul at i on syst em on t he def l ect i on syst ems boar d. I ' ve had 2 1970' s RCA' s wi t h t hi s pr obl em. ( C. P. H. ) . 9. 11)
I nt er mi t t ent j umpi ng or j i t t er i ng of pi ct ur e or ot her r andom behavi or
Thi s has al l t he cl ass i c sympt oms of a l oose connect i on i nt er nal t o t he TV or moni t or - pr obabl y wher e t he def l ect i on yoke pl ugs i nt o t he mai n PCB or at t he base of t he f l yback t r ansf or mer . TVs and moni t ors ar e not ori ous f or bot h poor qual i t y sol der i ng and bad connect i ons near hi gh wat t age component s whi ch j ust devel op over t i me f r om t emper at ur e cycl i ng. The f ol l owi ng i s not ver y sc i ent i f i c, but i t wor ks: Have you t r i ed whacki ng t he TV when t hi s happened and di d i t have any ef f ect ? I f yes, t hi s woul d be f ur t her conf i r mat i on of l oose connect i ons. What you need t o do i s exami ne t he sol der connect i ons on t he PCBs i n t he moni t or , par t i cul ar l y i n t he ar ea of t he def l ect i on ci r cui t s and power suppl y. Look f or hai r l i ne cr acks bet ween t he sol der and t he component pi ns - most l y t he f at pi ns of t r ansf or mer s, connect or s, and hi gh wat t age r esi st or s. Any t hat ar e f ound wi l l need t o be r ef l owed wi t h a medi um wat t age ( l i ke 40W) or t emper at ur e cont r ol l ed sol der i ng i r on. I t coul d al so be a component moment ar i l y br eaki ng down i n t he power suppl y or def l ect i on ci r c ui t s .
One ot her possi bi l i t y i s t hat t her e i s arci ng or cor ona as a resul t of humi d weat her . Thi s coul d t r i gger t he power suppl y t o shut down per haps wi t h a squeak, but t her e woul d pr obabl y be addi t i onal sympt oms i ncl udi ng possi bl y part i al l oss of br i ght ness or f ocus bef ore i t shut down. You may al so hear a si zzl i ng sound accompani ed by noi se or snow i n t he pi ct ur e, st at i c i n t he sounds, and/ or a smel l of ozone. 9. 12)
Hor i zont al out put t r ansi st or s keep bl owi ng
Unf or t unat el y, t hese sor t s of pr obl ems ar e of t en di f f i cul t t o def i ni t i vel y di agnose and r epai r - wi t h expensi ve component swappi ng. You have j ust r epl aced an obvi ousl y bl own ( shor t ed) hor i zont al out put t r ansi st or and an hour l at er , same sympt oms: Di d t he new t r ansi st or shor t ? Woul d t he next l ogi cal st ep be a new f l yback ( LOPT) ?
Not necessar i l y.
I f t he set per f or med nor mal l y unt i l i t di ed, t her e ar e ot her possi bl e causes. However , i t coul d be t he f l yback f ai l i ng under l oad or when i t war ms up. I woul d expect some war ni ng t hough - l i ke t he pi ct ur e shr i nks f or a f ew seconds bef ore t he poof . Ot her possi bl e causes: I nsuf f i ci ent dr i ve t o hor i zont al out put t r ansi st or ( HOT) . A weak dr i ve woul d cause t he HOT t o ei t her t ur n on or s hut of f t oo sl owl y gr eat l y i ncr easi ng heat di ssi pat i on. Check dr i ver and HOT base ci r cui t component s. Excessi ve vol t age on HOT col l ect or - check LV r egul at or ( and l i ne vol t age i f t hi s i s a f i el d r epai r ) , i f any. Def ect i ve saf et y capaci t or s or damper di ode ar ound HOT. ( Though t hi s us ual l y r es ul t s i n i ns t a nt des t r uc t i on wi t h l i t t l e heat i ng) . New t r ansi st or not mount ed pr oper l y t o heat si nk - pr obabl y needs mi ca washer and heat si nk compound. Repl acement t r ansi st or not cor r ect or i nf er i or cr oss r ef er ence. Somet i mes, t he hor i zont al def l ect i on i s desi gned based on t he qui r ks of a par t i cul ar t r ansi st or . Subst i t ut es may not wor k r el i abl y. The HOT shoul d not r un hot - pr oper l y mount ed t o t he heat si nk, i t shoul d not be t oo hot t o t ouch ( CAREFUL - don' t t ouch wi t h power on i t i s at over a hundr ed vol t s wi t h nast y mul t i hundr ed vol t spi kes and l i ne connect ed - di schar ge power suppl y f i l t er caps f i r st af t er unpl uggi ng) . I f i t i s scor chi ng hot af t er a f ew mi nut es, t hen you need t o check t he ot her possi bi l i t i es. I t i s al so possi bl e t hat a def ect i ve f l yback - per haps one shor t ed t ur n - woul d not cause an i mmedi ate f ai l ur e and onl y af f ect t he pi ct ur e sl i ght l y. Thi s woul d be unusual , however . See t he sect i on: Test i ng of f l yback ( LOPT) t r ansf or mer s. Not e t hat r unni ng t he set wi t h a ser i es l i ght bul b may al l ow t he HOT t o sur vi ve l ong enough f or you t o gat her some of t he i nf or mat i on needed
t o i dent i f y t he bad component . 9. 13)
Ver t i cal f ol dover
The pi ct ur e i s squashed ver t i cal l y and a par t of i t may be f l i pped over and di s t or t ed. Thi s usual l y i ndi cat es a f aul t i n t he ver t i cal out put ci r cui t . I f i t uses an I C f or t hi s, t hen t he chi p coul d be bad. I t coul d al so be a bad capaci t or or ot her component i n t hi s ci r cui t . I t i s pr obabl y caused by a f aul t i n t he f l yback por t i on of t he ver t i cal def l ect i on ci r cui t - a char ge pump t hat gener at es a hi gh vol t age spi ke t o r et ur n t he beam t o t he t op of t he scr een. Test component s i n t he ver t i cal out put st age or subst i t ut e f or good ones. 9. 14)
Squashed pi ct ur e on l at e model GE, RCA, or Pr oScan TV
( Fr om: dcavs@aol . com ( DCAVS) Sympt oms ar e a pi ct ur e t hat i s as wi de as t he scr een but t he ver t i cal hei ght i s compr essed. Pi ct ur e st ar t s about 1/ 3 of t he way down t he t ube and ext ends t o about 1/ 3 of t he way up f r om t he bot t om. Fur t her mor e, t he bot t om t r aces seem t o be over l ayed r esul t i ng i n br i ght er t han nor mal l i nes. Thi s i s a common pr obl em f or al l GE, RCA, Pr oScan t el evi si ons of a var i et y of chassi s. I t i s due t o a desi gn and manuf act ur i ng f l aw. You shoul d cal l RCA Cust omer Rel at i ons at 317- 587- 4151 and t ake i t t o a Thompson Aut hor i zed Ser vi cent er . ( Thompson El ect r oni cs of Fr ance owns t he names, RCA, GE, and Pr oScan f or Tel evi si ons. ) Thompson has been sendi ng t hei r cust omer s $75. 00 f or car r y i n ser vi ce and $95. 00 f or i n- home ser vi ce. Thi s amount shoul d cover t he bi l l as any t echni ci an who knows what t hey ar e doi ng shoul d be abl e t o compl et e t he r epai r s qui ckl y. Ther e i s a smal l chance t hat t he dat a i n t he e- pr om I C t hat st or es al l t he set up dat a has become cor r upt ed. I n t hi s case t he set needs t o be r e- pr ogr ammed t o oper at e cor r ect l y. Thi s i s a t i me consumi ng pr ocess and can have a gr eat af f ect on t he qual i t y of r ecept i on. 9. 15)
Pi ncushi oni ng Probl ems
I f t he l ef t and r i ght si des of t he pi ct ur e ar e bowed and t he scr een l ooks somet hi ng l i ke t he f ol l owi ng ( or t he opposi t e - bar r el di st or t i on: ============================================ \ / \ / \ / \ / \ / \ / | | | | | | / \ / \ / \ / \ / \ / \
============================================== Exami ne cl osel y your el ect r ol yt i c caps on t he mot her boar d f or l eaky ones. Al so l ook i nt o your hor z. ci r cui t r y to make sur e si gnal s and vol t ages ar e cor r ect. ( Gar y) I n par t i cul ar , t hi s sounds l i ke a pi ncushi on pr obl em - t o cor r ect f or pi ncushi on, a si gnal f r om t he ver t i cal def l ect i on t hat l ooks somet hi ng l i ke a rect i f i ed si newave i s used t o modi f y wi dt h based on ver t i cal posi t i on. Ther e i s usual l y a cont r ol t o adj ust t he magni t ude of t hi s si gnal and al so of t en, i t s phase. I t woul d seem t hat t hi s ci r cui t has ceased t o f uncti on. I f you have t he schemat i cs, check t hem f or ' pi ncushi on' adj ust ment s and check si gnal s and vol t ages. I f not , t r y t o f i nd t he ' pi ncushi on' magni t ude and phase adj ust ment s and l ook f or bad par t s or bad connect i ons i n i n t he gener al ar ea. Even i f t her e are no adj ust ment pots, t her e may st i l l be pi ncushi on cor r ecti on ci r cui t r y. I f t he i nt er nal cont r ol s have absol ut el y no ef f ect, t hen t he ci r cui t i s f aul t y. Wi t h moder n di gi t al set up adj ust ment s, t hen i t i s even t ougher t o di agnose si nce t hese cont r ol a D/ A somewher e l i nked vi a a mi cr opr ocessor . Pi ncushi on adj ust ment adds a si gnal t o t he hori zont al def l ect i on t o compensat e f or t he geomet r y of t he CRT/ def l ect i on yoke. I f you have knobs, t hen t r aci ng t he ci r cui t r y may be possi bl e. Wi t h l uck, you have a bad par t t hat can be i dent i f i ed wi t h an ohmmet er - shor t ed or open. However , wi t hout a schemati c even t hi s wi l l be di f f i cul t . I f t he adj ust ment s ar e di gi t al t hi s i s especi al l y di f f i cul t t o di agnose si nce you don' t even have any i dea of where t he ci r cui t r y woul d be l ocat ed. Faul t y capaci t or s i n t he hor i zont al def l ect i on power suppl i es of t en cause a si mi l ar set of sympt oms. 9. 16)
Test i ng of f l yback ( LOPT) t r ansf ormer s
How and why do f l yback t r ansf or mer s f ai l ? Fl ybacks f ai l i n sever al ways: Over heat i ng l eadi ng t o cr acks i n t he pl ast i c and exter nal ar ci ng. These can of t en be f i xed by cl eani ng and coat i ng wi t h mul t i pl e l ayer s of hi gh vol t age seal er , cor ona dope, or even pl ast i c el ect r i cal t ape (as a t empor ar y r epai r i n a pi nch) . Cr acked or ot her wi se damaged cor e wi l l ef f ect t he f l yback char act er i st i cs t o t he poi nt wher e i t may not wor k cor r ect l y or even bl ow t he hori zont al out put t r ans i s t o r . I nt er nal shor t s i n t he FOCUS/ SCREEN di vi der net work, i f pr esent . One si gn of t hi s may be ar cover of t he FOCUS or SCREEN spar kgaps on t he PCB on t he neck of t he CRT. I nt er nal shor t ci r cui t s i n t he wi ndi ngs. Open wi ndi ngs. Mor e t han one of t hese may appl y i n any gi ven case. Fi r st , per f or m a car ef ul vi sual i nspecti on wi t h power of f .
Look f or cr acks,
bul gi ng or mel t ed pl ast i c, and di scol or ati on, Look f or bad sol der connect i ons at t he pi ns of t he f l yback as wel l . I f t he TV or moni t or can be powered saf el y, check f or ar ci ng or cor ona ar ound t he f l yback and i n i t s vi ci ni t y, Next, per f orm ohmmet er t est s f or obvi ous shor t ci r cui t s bet ween wi ndi ngs, much r educed wi ndi ng r esi st ances, and open wi ndi ngs. For t he l ow vol t age wi ndi ngs, ser vi ce manual s may pr ovi de t he expect ed DC r esi st ance ( SAMs Phot oFact , f or exampl e) . Somet i mes, t hi s wi l l change enough t o be det ect ed - i f you have an ohmmet er wi t h a l ow enough scal e. These ar e usual l y a f r act i on of an ohm. I t i s di f f i cul t or i mpossi bl e t o measur e t he DC r esi st ance of t he HV wi ndi ng si nce t he r ect i f i er s ar e usual l y bui l t i n. The val ue i s not publ i shed ei t her . CAUTI ON: make sur e you have t he TV or moni t or unpl ugged and conf i r m t hat t he mai n f i l t er capaci t or i s di schar ged bef or e t ouchi ng anythi ng! I f you ar e goi ng t o r emove or t ouch t he CRT HV, f ocus, or scr een wi r es, di schar ge t he HV f i r st usi ng a wel l i nsul at ed hi gh val ue r esi st or ( e. g. , sever al M ohms, 5 W) t o t he CRT gr ound st r ap ( NOT si gnal gr ound. See t he sect i on: Saf e di schargi ng of capaci t or s i n TVs and vi deo moni t ors. Par t i al l y shor t ci r cui t ed wi ndi ngs ( per haps, j ust a coupl e of t ur ns) and somet i mes shor t s i n t he f ocus/ scr een di vi der wi l l dr ast i cal l y l ower t he Q and i ncr ease t he l oad t he f l yback put s on i t s dr i vi ng sour ce wi t h no out put s connect ed. Commer ci al f l yback t est er s measur e t he Q by moni t or i ng t he decay t i me of a r esonant ci r cui t f ormed by a capaci t or and a wi ndi ng on t he f l yback under t est af t er i t i s exci t ed by a pul se wavef or m. I t i s possi bl e t o easi l y const r uct t est er s t hat per f or m a wel l . See t he compani on document Test i ng of Fl yback ( LOPT) Tr ansf or mer s f or f ur t her i nf or mat i on. Chapt er 10) 10. 1)
Hi gh Vol t age Power Suppl y Pr obl ems
HV power suppl y f undament al s
Most , i f not al l , TVs der i ve t he hi gh vol t age f or t he CRT second anode, f ocus, and ( somet i mes) scr een ( G2) f r om t he hor i zont al def l ect i on syst em. Thi s t echni que was devel oped qui t e ear l y i n t he hi st or y of commer ci al TV and has st uck f or a ver y si mpl e r eason - i t i s ver y cost ef f ect i ve. A si de ef f ect i s that i f t he hor i zont al def l ecti on f ai l s and t hr eat ens to bur n a ( ver t i cal ) l i ne i nt o the CRT phosphor s, t he hi gh vol t age di es as wel l . Most TV hi gh vol t age suppl i es oper at e as f ol l ows: Hor i zont al out put t r ansi st or ( HOT) t ur ns on dur i ng scan. Cur r ent i ncr eases l i near l y i n pr i mar y of f l yback tr ansf or mer si nce i t appear s as an i nduct or . Magnet i c f i el d al so i ncreases l i near l y. NOTE: f l yback i s const r uct ed wi t h ai r gap i n cor e. Thi s makes i t behave more l i ke an i nduct or as f ar as the pr i mar y dr i ve i s concer ned. HOT shut s of f at end of scan. Cur r ent decr eases rapi dl y. Magnet i c f i el d col l apses i nduct i vel y coupl i ng t o secondar y and gener at es HV pul se. I nduct ance and capaci t ance of f l yback, snubber capaci t or s, and par asi t i c capaci t ance of ci r cui t r y and yoke f or m a r esonant ci r cui t . I deal l y, vol t age wavef or m acr oss HOT dur i ng f l yback ( r et r ace) per i od wi l l be a si ngl e hal f cycl e and i s cl amped by damper di ode acr oss HOT t o pr event under shoot .
Secondar y of f l yback i s ei t her a si ngl e l ar ge HV wi ndi ng wi t h HV r ect i f i er s bui l t i n ( most of t en) or an i nt er medi at e vol t age wi ndi ng and a vol t age mul t i pl i er ( see t he secti on: What i s a t r i pl er . ) The out put wi l l be DC HV pul ses. The capaci t ance of t he CRT envel ope pr ovi des t he needed f i l t er i ng t o adequat el y smoot h t he HV pul ses i nt o a DC vol t age. A hi gh resi st ance vol t age di vi der pr ovi des t he sever al KV f ocus vol t age and somet i mes t he sever al hundr ed vol t scr een ( G2) vol t age as wel l . Of t en, t he adj ust ment s f or t hese vol t ages are bui l t i nt o the f l yback. Somet i mes t hey ar e mount ed separ at el y. 10. 2)
What i s a t r i pl er ?
I n some TVs, t he f l yback t r ansf or mer onl y gener at es about 6- 10 KV AC whi ch i s t hen boost ed by a capaci t or - di ode l adder t o t he 18- 30 KV needed f or moder n col or CRTs. The uni t t hat does t hi s i s commonl y cal l ed a t r i pl er si nce i t mul t i pl i es t he f l yback out put by about 3 t i mes. Some TVs use a quadr upl er i nst ead. However , many TVs gener at e t he r equi r ed HV di r ect l y wi t h a wi ndi ng wi t h t he requi r ed number of t ur ns i nsi de t he f l yback t r ansf or mer . Tr i pl er s use a di ode- capaci t or l adder t o mul t i pl y t he 6- 10 KV AC t o 18- 30 KV DC. Many t r i pl er s are separ at e uni t s, r oughl y cubi cal , and ar e not r epai r abl e. Some t r i pl er s ar e bui l t i n t o t he f l yback - i t i s pr obabl y cheaper t o manuf act ur e t he HV di odes and capaci t or s t han t o wi nd a di r ect hi gh vol t age secondar y on t he f l yback cor e. I n ei t her case, f ai l ur e r equi r es repl acement of t he ent i r e uni t . For external mul t i pl i er s, t he t er mi nal s ar e t ypi cal l y mar ked: I N - f r om f l yback ( 6- 10 KV AC) . OUT - HV t o CRT ( 20- 30 KV DC) . F - f ocus t o CRT (2- 8 KV) . CTL - f ocus pot ( many megohm t o gr ound) . G, GND, or COM - gr ound. Sympt oms of t r i pl er f ai l ur e ar e: l ack of hi gh vol t age or i nsuf f i ci ent hi gh vol t age, ar ci ng at f ocus pr ot ect i on spar k gap, i ncor r ect f ocus vol t age, ot her arci ng, over l oad of HOT and/ or f l yback, or f ocus adj ust ment af f ect i ng br i ght ness (scr een) set t i ng or vi ce- ver sa. 10. 3)
Hi gh vol t age shut down due t o X- r ay pr otect i on ci r cui t s
A TV t hat r uns f or a whi l e or st ar t s t o come on but t hen shut s down may have a pr obl em wi t h t he X- r ay pr ot ecti on ci r cui t r y cor r ectl y or i ncor r ectl y det er mi ni ng t hat t he hi gh vol t age ( HV) i s t oo gr eat ( r i ski ng excessi ve X- r ay emi ssi on) and shut t i ng ever yt hi ng down. A si de ef f ect of acti vat i on of t hi s ci r cui t r y i s t hat r eset t i ng may r equi r e pul l i ng t he pl ug or t ur ni ng of f t he r eal ( har d) power swi t ch. I s t her e anythi ng el se unusual about t he pi ct ur e l at el y t hat woul d i ndi cat e an act ual pr obl em wi t h t he HV? I f t hi s i s t he case, t hen t her e may be some pr obl em wi t h t he HV r egul at i on. I f not , t he shut down ci r cui t may be over l y sensi t i ve or one of i t s component s may be def ect i ve - a bad connect i on of l eaky cap ( or zener ) .
One sympt om of excessi ve HV ( but not r equi r ed) i s an over l y br i ght pi ct ur e of r educed si ze. The HV shut down ci r cui t usual l y moni t or s a wi ndi ng of f of t he f l yback f or vol t age exceedi ng some r ef er ence and t hen set s a f l i p f l op shut t i ng t he hor i z ont al dr i ve of f . On some Sony model s, a HV r esi st i ve di vi der per f or ms t hi s f unct i on and t hese do f ai l - qui t e of t en. The r ed bl ock cal l ed a ' HV capaci t or' i s a common cause of i mmedi at e or del ayed shut down on cer t ai n Sony moni t or s and TVs. 10. 4)
Low or no hi gh vol t age
Most of t hese pr obl ems ar e due t o f aul t s i n t he hor i zont al def l ect i on syst em - shor t ed HOT, shor t ed wi ndi ngs or HV r ect i f i er s i n the f l yback, def ect i ve t r i pl er , or ot her bad par t s on t he pr i mar y si de of t he f l yback. However , i f you di scover an i nch l ayer of f i l t h i nsi de t he TV, t he HV coul d si mpl y be shor t i ng out - cl ean i t f i r st . I n most cases, t hese sor t s of f aul t s wi l l put an excessi ve l oad on t he hori zont al out put ci r cui t s so t her e may be excessi ve heat i ng of t he HOT or ot her component s. You may hear an audi bl e ar ci ng or si zzl i ng sound f r om i nt er nal shor t s i n t he f l yback or t r i pl er . Ei t her of t hese may bet hot , cr ack, bul ge, or exhi bi t vi si bl e damage i f l ef t on wi t h t he f aul t pr esent . Most moder n TVs do not r egul at e HV di r ect l y but r at her set i t vi a cont r ol of t he l ow vol t age power suppl y t o t he HOT ( B+) , by snubber capaci t or s acr oss t he HOT, and t he t ur ns r at i o of t he f l yback. The HV i s di r ect l y r el at ed t o t he B+ so i f t hi s i s l ow, t he HV wi l l be l ow as wel l . Faul t y snubber capaci t or s wi l l gener al l y do t he opposi t e - i ncr ease t he HV and t he X- r ay pr ot ect i on ci r cui t s may ki ck i n. However , l ow HV i s al so a possi bi l i t y. The onl y way t he t ur ns rat i o of t he f l yback can change i s f r om a short whi ch wi l l mani f est i t s pr esence i n ot her ways as wel l - excessi ve heat i ng and l oad on t he hor i zont al out put ci r cui t s. Whi l e a shor t ed second anode connect i on t o t he CRT i s t heor et i cal l y possi bl e, t hi s i s qui t e unl i kel y ( except , as not ed, due t o di r t ) . 10. 5)
Excessi ve hi gh vol t age
Any si gni f i cant i ncr ease i n HV shoul d cause t he X- r ay pr ot ect i on ci r cui t s t o ki ck i n and ei t her shut down t he set or modi f y t he def l ect i on i n such a way as t o r ender i t har ml ess. Sympt oms i ncl ude ar ci ng/ spar ki ng of HV, smal l er t han nor mal pi ct ur e, and under cer t ai n scenar i os, possi bl e excessi ve br i ght ness. Causes of t he HV bei ng t oo hi gh ar e: Excess B+ vol t age t o t he HOT. r egul at or f ai l ur e .
The l i kel y cause i s t o a l ow vol t age
Open snubber capaci t or s acr oss t he HOT. These ar e under a l ot of st r ess and ar e l ocat ed near hot component s so f ai l ur e i s possi bl e. I ncor r ect excessi vel y l ong scan dr i ve t o HOT caused by f ai l ur e of
hor i zont al osci l l at or / sync ci r cui t s. However , ot her t hi ngs l i ke t he HOT wi l l pr obabl y bl ow up f i r st . The pi ct ur e wi l l def i ni t el y be messed up. Fai l ur e of HV r egul at or ( t ube set s and a f ew sol i d st at e set s - act ual HV r egul at ors ar e r el at i vel y uncommon t oday. ) Thi s may r esul t i n an under scanned ( smal l er t han normal ) pi ct ur e. 10. 6)
Ar ci ng, spar ki ng, or cor ona f r om CRT HV anode ( r ed wi r e/ suct i on cup)
Sympt oms coul d i ncl ude a si zzl i ng corona or more l i kel y, an occasi onal or r api d ser i es of shar p snaps - possi bl y qui t e l oud and qui t e vi si bl e - f r om t he anode cap on t he CRT t o t he gr ounded coat i ng on t he out si de of t he CRT or a chassi s gr ound poi nt ( or any ot her conduct or nearby) . Cor ona i s a hi gh r esi st ance l eakage t hr ough t he ai r wi t hout t ot al br eakdown. The snappi ng i s c aused by t he sudden and near l y compl et e di schar ge of t he CRT anode capaci t ance t hr ough a l ow r esi st ance i oni zed pat h si mi l ar t o l i ght eni ng. Ther e ar e t wo l i kel y causes : Di r t , dust , gr i me, ar ound and under t he suct i on cup on t he CRT ar e pr ovi di ng a di schar ge pat h. Thi s may be mor e sever e i n humi d weat her . Saf el y di schar ge t he HV and t hen r emove and t hor oughl y cl ean t he HV suct i on cup and t he ar ea under i t and on t he CRT f or sever al i nches ar ound t he HV connect i on. Make sur e t her e ar e no l oose wi r es or ot her possi bl e pl aces f or t he HV t o di schar ge t o i n t he vi ci ni t y. The hi gh vol t age has gone t hr ough t he r oof . Usual l y, t he X- r ay pr ot ect i on c i r c ui t r y s houl d ki c k i n but i t c an f ai l . I f c l eani ng does not hel p, t hi s i s a l i kel y pos si bi l i t y. See t he s ec t i ons : Hi gh vol t age shut down due t o X- r ay pr ot ect i on ci r cui t s and Excessi ve hi gh vol t age. 10. 7)
Ar ci ng at CRT spar kgaps
Thi s i s r ar el y due t o a def ect i ve spar kgap but r at her i s a saf et y mechani sm l i ke a f use desi gned to pr ot ect t he i nt er nal el ect r odes of t he CRT i f t he f ocus or s cr een vol t age shoul d become excess i ve. The spar kgap br eaks down f i r st and pr event s i nt er nal ar ci ng i n t he CRT. An arci ng spar kgap i s usual l y accompani ed by t ot al l oss of pi ct ur e or bad f ocus, br i ght ness or f ocus f l uct uat i ons, or any of a number of si mi l ar sympt oms. The usual cause i s a br eakdown i nsi de t he f ocus di vi der i nsi de t he f l yback or t r i pl er . Somet i mes, i t i s i n a component t hat can be di sassembl ed and cl eaned but not gener al l y. Repl acement of t he bad par t wi l l be needed. 10. 8)
Ar c i ng f r om f l ybac k or vi c i ni t y
I f t he ar c i s comi ng f r om a speci f i c poi nt on t he f l yback - a cr ack or pi nhol e - t hi s may be pat ched usi ng hi gh vol t age seal er or even a f ew l ayer s of pl ast i c el ect r i cal t ape. Thi s may pr ove t o be a per manent r epai r al t hough st ar t i ng t he sear ch f or a sour ce f or a new f l yback woul d not hur t j ust i n case. The ar c most l i kel y di d damage t he i nsul at i on i nt er nal l y whi ch may or may not be a pr obl em i n t he f ut ur e. I n some cases, t he pi nhol e or cr ack i s an i ndi cat i on of a more ser i ous
pr obl em - over heat i ng due t o shor t ed wi ndi ngs i n t he f l yback or excessi ve secondary l oad. Fi r st , cl ean t he ar eas ar ound the arc t hor oughl y and t hen t r y sever al l ayer s of pl ast i c el ectr i cal t ape. I f t he TV wor ks nor mal l y f or say, an hour , t hen t her e i s pr obabl y not hi ng el se wr ong and you can t r y f or a pr oper seal i ng j ob or hope t hat t ape hol ds out ( put a f ew more l ayers on - each i s good f or about 8- 10 KV t heoret i cal l y) . I f t he ar c i s f r om one of t he spar kgaps around t he CRT, t hi s coul d al so be a f l yback pr obl em i ndi cat i ng i nt er nal shor t s i n t he f ocus/ screen net wor k. Once I had a TV wher e t he mai n pr obl em was a cr acked f l yback ar ci ng but t hi s t ook out one of t he f usabl e r esi st or s f or t he power suppl y t o t he VERTI CAL out put so t he sympt oms i ncl uded a si ngl e hori zont al l i ne. Don' t ask me t o expl ai n - r epl aci ng t hat r esi st or and t he f l yback (t he f l yback t est ed good, but t hi s was f or someone el se) f i xed t he TV. I n anot her case, a pi nhol e devel oped i n t he f l yback casi ng pr obabl y due t o poor pl ast i c mol di ng at t he t i me of manuf act ur e. Thi s r esul t ed i n a most spect acul ar case of spar ki ng t o a near by br acket . A f ew l ayer s of el ect r i cal t ape was al l t hat was needed to af f ect a per manent r epai r . 10. 9)
Ozone smel l and/ or smoke f r om TV
Smoki ng i s j ust as bad f or TVs as f or peopl e and usual l y mor e qui ckl y t er mi nal . Whi t e acr i d smoke may i ndi cat e a f ai l ed el ect r ol yt i c capaci t or i n t he power suppl y pr obabl y i n conj unct i on wi t h a shor t ed r ect i f i er . Needl ess t o say, pul l t he pl ug at once. A vi sual i nspect i on shoul d be abl e t o easi l y conf i r m t he bad capaci t or as i t wi l l pr obabl y be bul gi ng and have condensed r esi due near by. Check t he r ect i f i er di odes or br i dge r ect i f i er wi t h an ohmmet er . Resi st ance acr oss any pai r of l eads shoul d be mor e t han a f ew ohms i n at l east one di r ect i on. Remove f r om t he ci r cui t t o conf i r m. Bot h t he f aul t y di ode( s) and capaci t or shoul d be r epl aced ( t hough t he capaci t or may wor k wel l enough t o t est wi t h new di ode( s) . I f a vi sual i nspect i on f ai l s t o i dent i f y the smoki ng par t , you can pr obabl y pl ug t he set i n f or a f ew seconds unt i l t he sour ce of t he smoke i s obvi ous but be pr epar ed t o pul l t he pl ug i n a r eal hur r y. I f t he smel l / smoke i s comi ng f r om t he f l yback, t hen i t has probabl y gone bel l y up. You may be abl e t o see a cr ack or bul ge i n t he case. Whi l e t he f l yback wi l l def i ni t el y need t o be r epl aced, i t i s l i kel y t hat not hi ng el se i s wr ong. However , i t mi ght be pr udent t o use a Var i ac when per f or mi ng i ni t i al t est i ng wi t h t he repl acement j ust i n case t her e i s a secondar y shor t ci r cui t or excess HV pr obl em. 10. 10)
Shoul d I be worr i ed about X- r ay exposur e whi l e servi ci ng a TV or moni t or?
The onl y sour ce of X- r ays i n a moder n TV or moni t or i s f r om t he CRT. X- r ays ar e gener at ed when a hi gh vel oci t y el ect r on bean st r i kes a heavy met al t ar get . For anythi ng you ar e l i kel y t o encount er , t hi s can onl y happen i n a vacuum - t hus i nsi de t he CRT. The hi gher t he vol t age, t he gr eat er t he vel oci t y and pot ent i al danger .
The t hi ck f r ont CRT f acepl at e pr ot ect s user s adequat el y but t her e may be some emi ssi on f r om t he t hi nner si des. At 25- 30 KV ( qui t e l ow as X- r ay ener gi es go) X- r ays wi l l be st opped by al most any met al so what you have t o wor r y about i s wher e t her e are no shi el ds. However , r eal i st i cal l y, t her e i s ver y l i t t l e and I woul d not wor r y about exposur e unl ess you pl an to be si t t i ng f or hour s on t he si des, behi nd, or under t he TV or moni t or - wi t h a pi ct ur e ( t her e wi l l be none i f t he scr een i s bl ack) . 10. 11)
Fl yback shot by 4 year ol d
Your 4 year ol d son shot t he Sony i n t he f l yback t r ansf or mer . Smoke and spar ks ever ywher e. Gr eat ai m! Who says t hese FAQs cannot be f unny? Needl ess t o say, unpl ug t he set i mmedi at el y. I nspect around t he t arget ar ea f or obvi ousl y bl own or damaged component s. Test f uses and f usabl e r esi st or s. Repai r bur nt sol der connect i ons and ci r cui t boar d t r aces. Once t he set i s ent i r el y dr i ed out , power i t up - pr ef er abl y t hr ough a ser i es l i ght bul b and/ or Var i ac unt i l you ar e sur e not hi ng el se wi l l l et l oose. Look, l i st en, and smel l f or any unusual behavi or . I f i t now wor ks, t hen consi der your sel f l ucky. I f not , t her e may be damage t o t r ansi st or s, I Cs, or ot her component s. ( The f ol l owi ng f r om: edi son@nel son. pl anet . org. nz ( Ri chard Symonds) ) . We' r e seei ng anot her ' hazar d' t hese days, peopl e cl eani ng t hei r t el evi si on scr eens wi t h wi ndow cl eaner - no pr obl em i n the days of separ at e chassi s but wi t h t he ent i r e p. c. b. j ammed under t he t ube on most t . v. s t hese days j ust a f ew dr i ps and i t s al l over. Some have j ust cor r oded t he swi t ch banks ( had one r ecent l y j ust got i nt o t he A/ V swi t ch - when you wal ked ar ound t he r oom t he set changed t o A/ V and back by i t sel f ! ) but a f ew have got ar ound t he mi cr opr ocessor s and surf ace mount component s and r esul t ed i n compl et e wr i t e- of f s. I suppose t he damage i s t he opposi t e of el ect r opl at i ng as t he mi cr op' s have const ant vol t age t o t hem. Never mi nd, t hey' l l be a good sour ce of par t s f or f ut ur e use. Chapt er 11) 11. 1)
Rast er , Col or , and Vi deo Pr obl ems
No col or - bl ack and whi t e pi ct ur e
Thi s means absol ut el y no col or - equi val ent t o a bl ack and whi t e pi ct ur e. Not even a hi nt of col or . Fi r st , conf i r m t hat t he sour ce i s actual l y i n col or - t r y anot her channel or i nput devi ce. Next, check t he set t i ngs of t he col or cont r ol - i t may have acci dent al l y been t ur ned down. I f your TV has some ki nd of aut omat i c pi ct ur e mode, t r y t ur ni ng i f of f and adj ust i ng t he col or cont r ol . Tr y adj ust i ng f i ne t uni ng i f you have such a cont r ol and t he pr obl em i s wi t h a br oadcast or cabl e tr ansmi ssi on.
At t hi s poi nt wi t h a conf i r med col or si gnal sour ce, t her e i s a pr obl em wi t h t he chr oma ci r cui t r y. Not e t hat t o t he aver age per son, t he obvi ous quest i on becomes: i s my col or pi ct ur e t ube bad? The answer i s a def i ni t i ve NO. I t i s vi r t ual l y i mpossi bl e f or a def ect i ve CRT t o cause a t ot al l oss of col or. A def ect i ve CRT can cause a l ack of a pr i mar y col or - R, G, or , B whi ch wi l l mess up the col or but i s not l i kel y t o r esul t i n a bl ack and whi t e pi cture. Some possi bi l i t i es i n no par t i cul ar or der : Weak si gnal or def ect i n t uner / I F causi ng l oss of si gnal st r engt h. Col er ki l l er s et t oo hi gh ( i nt er nal c ont r ol ) i f i t has one. Def ect i ve par t around t he chr oma chi p/ ci r cui t . Faul t y col or osci l l at or . Bad connect i ons i n ar ea of chr oma chi p/ ci r cui t . Def ect i ve chr oma chi p ( don' t suspect t hi s f i r st j ust because i t i s pr obabl y ver y expensi ve) . A ser vi ce manual or SAMs, DMM, & scope wi l l hel p gr eat l y i n at t empt i ng t o t r oubl eshoot t hi s unl ess i t i s an obvi ous bad connect i on. Tr y pr oddi ng t he mai n boar d ar ound t he chr oma chi p wi t h an i nsul at ed t ool t o see i f you can make t he col or come and go. I had one set wher e a $. 02 r esi st or deci ded t o open up causi ng j ust t hi s pr obl em - per f ect BW pi ct ur e, no col or . Anot her had a coi l wi t h a br oken wi r e. 11. 2)
Psychodel i c col or
The means col or s t hat ar e not nor mal and t hat adj ust ment of t he user cont r ol s i s not abl e t o cor r ect i t so t hat al l col or s of t he pi cture ar e pr oper l y di spl ayed at t he same t i me. For exampl e, you ar e unabl e t o get any yel l ows or bl ues i n scenes t hat shoul d have t hese col or s. . Make sure t he user col or and t i nt cont r ol s have not been acci dent al l y t ur ned whi l e cl eani ng or pur posedl y mi sadj ust ed by smal l ( or l ar ge) ki ds. Per f or m t he user set up descr i bed i n t he sect i on: User pi ct ur e adj ust ment . Conf i r m t hat t he sour ce i s not a wei r d col or vi deo - t r y anot her channel or a t ape. Ver i f y that t hi s i s not a mi ssi ng col or pr obl em - one of t he pr i mar y R, G, or B, has di sappear ed. I f so, r ef er t o t he sect i on: Mi ssi ng col or s. Once t hese have been el i mi nat ed, you ar e l ef t wi t h t he f ol l owi ng pos si bi l i t i es : Def ect i ve par t ar ound t he chr oma chi p/ ci r cui t . Mi sadj ust ed col or os ci l l at or . Bad connect i ons i n ar ea of chr oma chi p/ ci r cui t . Def ect i ve chr oma chi p ( don' t suspect t hi s f i r st j ust because i t i s pr obabl y ver y expensi ve) . A ser vi ce manual or SAMs, DMM, & scope wi l l hel p gr eat l y i n at t empt i ng t o t r oubl eshoot t hi s unl ess i t i s an obvi ous bad connect i on. Tr y pr oddi ng
t he mai n boar d ar ound t he chr oma chi p wi t h an i nsul at ed t ool t o see i f you can r est ore normal col or. Somet hi ng as si mpl e as a bad r esi st or or i nduct or can be t he cause - don' t i mmedi at el y suspect t he most expensi ve par t . 11. 3)
TV and Moni t or Manuf act ur i ng Qual i t y and Col d Sol der J oi nt s
Any i nt er mi t t ent pr obl ems wi t h moni t or s t hat cause r andom sudden changes i n t he pi ctur e br i ght ness, col or , si ze, or posi t i on ar e of t en a r esul t of bad connect i ons. Bad sol der j oi nt s ar e ver y common i n TVs and moni t or s due bot h t o poor qual i t y manuf act ur i ng as wel l as t o det er i or at i on of t he sol der bond af t er numer ous t her mal cycl es and component s r unni ng at hi gh t emper at ur e. Wi t hout knowi ng anyt hi ng about t he ci r cui t r y, i t i s usual l y possi bl e t o cur e t hese pr obl ems by l ocat i ng al l bad sol der connect i ons and cl eani ng and r eseat i ng i nt er nal c onnec t or s . The t er m ' c ol d s ol der j oi nt ' s t r i c t l y r ef er s t o a s ol der connect i on t hat was ei t her not heat ed enough dur i ng manuf act ur i ng, was cool ed t oo qui ckl y, or wher e par t pi ns wer e moved bef or e t he sol der had a chance t o sol i di f y. A si mi l ar si t uat i on can devel op over t i me wi t h t her mal cycl i ng wher e par t s ar e not pr oper l y f ast ened and ar e essent i al l y bei ng hel d i n by t he sol der al one. Bot h si t uat i ons ar e most common wi t h t he pi ns of l arge component s l i ke t r ansf ormer s, power t r ansi st or s and power r esi st or s, and l ar ge connect or s. The pi ns of t he component s have a l ar ge t her mal mass and may not get hot enough dur i ng manuf act ur i ng. Al so, t hey ar e r el at i vel y massi ve and may f l ex t he connect i on due t o vi br at i on or t hermal expansi on and cont r act i on. To l ocat e col d sol der j oi nt s, use a st r ong l i ght and magni f i er and exami ne t he pi ns of l ar ge component s f or hai r l i ne cr acks i n t he sol der around the pi n. Gent l y wi ggl e t he component i f possi bl e ( wi t h t he power of f ) . Any det ect abl e movement at t he j oi nt i ndi cat es a pr obl em. Wi t h t he power on, gent l y pr od t he ci r cui t boar d and suspect component s wi t h an i nsul at ed t ool t o see i f t he pr obl em can be ef f ect ed. When i n doubt , r esol der any suspi ci ous connect i ons. Some moni t or s may use doubl e si ded ci r cui t boar ds whi ch do not have pl at ed t hr ough hol es. I n t hese cases, sol der bot h t op and bot t om t o be sur e t hat t he connect i ons are sol i d. Use a l arge enough sol der i ng i r on t o assur e t hat your sol der connect i on i s sol i d. Put a bi t of new sol der wi t h f l ux on ever y connect i on you t ouch up even i f t her e was pl ent y of sol der t her e bef or e. 11. 4)
I nt er mi t t ent or Mi ssi ng Col or s
I f gent l y whacki ng t he set can make t he col or ( s) come and go, t hen bad connect i ons ar e a ver y l i kel y possi bi l i t y. The t he ef f ect i s sudden - t he col or dr ops i n and out i nst ant l y, i t i s not a CRT pr obl em. I f t he col or f ades i n and out wi t h a del ay of about 10- 15 seconds, i t i s pr obabl y i nt er mi t t ent power t o t he CRT f i l ament f or t hat col or and pr obabl y means a bad CRT si nce t he t hr ee f i l ament s ar e wi r ed i n paral l el i nsi de t he CRT and one of t he i nt er nal connect i ons has come l oose. Look i n t he neck of t he CRT t o make sur e al l t hr ee f i l ament s ar e gl owi ng or ange. I f one i s out or goes on and of f t oss t he set .
Repl aci ng t he CRT i s pr obabl y not wor t h i t . However , i f t hey al l go on and of f t oget her ( al l col or s woul d be f adi ng i n and out t hough per haps not qui t e i n uni son) , t hen bad connect i ons on t he vi deo dr i ver boar d ( on t he neck of t he CRT) ar e i ndi cat ed. Locat e t he out put f or t he bad col or on t he vi deo dr i ver boar d on t he neck of t he CRT. Thi s wi l l pr obabl y r ead a si gni f i cant l y hi gher vol t age t han t he cor r espondi ng pi ns f or t he good col or s. A ci r cui t pr obl em i s l i kel y - pr obabl y on t hi s boar d. Test component s on t hi s boar d f or t he good and bad col or channel s. short ed t r ansi st or or open r esi st or can ki l l one channel . Swap par t s t o conf i r m.
A
Thi s i s a cat ch- al l f or some of t he most common TV and moni t or pr obl ems. Most of t he causes of i nt er mi t t ent col or s boi l down t o bad connect i ons of one f or m or anot her . For t ot al l y dead col or s - not i nt er mi t t ent - bad component s ar e al so a possi bi l i t y. Pri nt ed ci r cui t boar d on t he CRT neck. Thi s i s a common l ocat i on f or col d sol der j oi nt s. Check wi t h a br i ght l i ght and magni f yi ng gl ass f or hai r l i ne cracks ar ound t he pi ns of l ar ger par t s. Pr od and t ap wi t h an i nsul at ed t ool t o see i f t he pr obl em i s ef f ected. Resol der i f necessar y. Col d sol der j oi nt s el sewher e i n TV or moni t or usual l y ar ound t he pi ns of l ar ge part s such as t r ansf ormer s, power t r ansi st or s and r esi st or s, and i nt er nal connect or s. I nt er nal connect or s t hat need t o be cl eaned and r eseat ed. cl ean wi t h cont act cl eaner , bur ni sh, and r epl ace. 11. 5)
Remove,
Red, gr een, or bl ue f ul l on - f og over pi ct ur e
Thi s coul d be a heat er - cat hode ( H- K) shor t i n t he CRT or a f ai l ur e of a component i n t he chr oma ci r cui t s or vi deo out put ( dr i ver boar d) . Don' t pani c - heat er - cat hode shor t s i n CRTs can of t en be wor ked ar ound. Some si mpl e t est s can conf i r m or r ul e out ot her possi bi l i t i es. Compar e the vol t ages f or t he vi deo dr i ve si gnal s t o t he CRT on t he l i t t l e boar d on t he neck of t he CRT wi t h t he CRT bot h connect ed and unpl ugged. A schemat i c wi l l hel p gr eat l y i n l ocat i ng t hese si gnal s. I f t her e i s a si gni f i cant di f f er ence especi al l y on t he bad col or , t hen t he CRT i s a l i kel y candi dat e. Tr y t appi ng t he neck of t he CRT GENTLY ( wi t h i t pl ugged i n and whi l e vi ewi ng a pi ct ur e) t o see i f i t i s an i nt er mi t t ent pr obl em. Mi ght want t o have eye pr ot ect i on on whi l e doi ng t hi s! I f t her e i s no si gni f i cant di f f er ence, you may have a bad dr i ver or a pr obl em i n t he chr oma ci r cui t s. Look f or bad connect i on/ col d sol der j oi nt s, pr obabl y on t he l i t t l e boar d on t he neck of t he CRT. Use an i nsul at ed st i ck t o gent l y pr od t he boar d and i t s component s i n an ef f or t t o i nduce/ cur e t he pr obl em. Look car ef ul l y f or hai r l i ne cr acks ar ound the component l eads.
You can swap component s bet ween t wo col or s and/ or t est wi t h an ohmmet er on t hat dr i ver boar d t o det er mi ne what i s bad. The ni ce t hi ng about col or moni t ors and TVs i s t hat t her e t hr ee copi es of each of t hese component s. Swappi ng and/ or compar i sons bet ween t hese i s an excel l ent di agnosti c t echni que. Al t er nat i vel y, i nt er change t he out put s of t he bad col or wi t h a good one by j umper i ng on t he vi deo dr i ver boar d ( on t he CRT neck) . I f t he bad col or changes, t hen t he pr obl em i s i n t he ci r cui t r y and not t he CRT. 11. 6)
Pr ovi di ng i sol at i on f or a CRT H- K shor t
Thi s pr ocedur e wi l l subst i t ut e a wi ndi ng of your own f or t he one t hat i s bui l t i n t o t he f l yback t o i sol at e t he shor t ed f i l ament f r om t he gr ound or vol t age r ef er ence. Not e t hat i f you have a schemat i c and can det er mi ne wher e t o di sconnect t he gr ound or vol t age r ef er ence connect i on t o t he f i l ament wi ndi ng, t r y t hi s i nst ead. The f l yback i s t he t hi ng wi t h t he f at r ed wi r e comi ng out of i t ( and per haps a coupl e of ot hers goi ng t o t he CRT boar d or i t i s near t hi s component i f your set has a separ at e t r i pl er ) and may have a coupl e of cont r ol s f or f ocus and scr een. I t shoul d have some exposed par t s wi t h a f er r i t e core about 1/ 2- 3/ 4 di amet er . The f i l ament of t he CRT i s t he i nt er nal heat er f or each gun - i t i s what gl ows or ange when t he set i s on. What has happened i s t hat a par t of t he f i ne wi r e of t he bad col or' s f i l ament ( assumi ng t hi s i s i ndeed your pr obl em) has shor t ed t o t he cat hode - t he part t hat act ual l y emi t s t he el ect r ons. Nor mal l y, t he heat er ci r cui t i s gr ounded or t i ed t o a r ef er ence vol t age so when i t shor t s t o t he cat hode, t he cat hode vol t age l evel i s pul l ed t o gr ound or t hi s r ef er ence. You wi l l need some wel l i nsul at ed wi r e, f ai r l y t hi ck ( say #18- 22) . Fi nd a spot on t he f l yback wher e you can st i ck t hi s ar ound t he cor e. Wr ap t wo t ur ns around t he cor e and sol der t o t he CRT f i l ament pi ns af t er cut t i ng t he connect i ons t o t he ori gi nal f i l ament sour ce ( scr i be t he t r aces on t he board t o br eak t hem) . Thi s wi ndi ng shoul d cause t he f i l ament s t o gl ow about t he same br i ght ness as bef ore but now i sol at ed f r om gr ound. I f t hey are t oo di m, put anot her t ur n on t he f l yback t o boost t he vol t age. ( Don' t go over boar d as you may bl ow t he f i l ament t ot al l y i f you put t oo many t ur ns on t he cor e - you t hen t oss t he TV. ) Rout e t he wi r es so t hat t her e i s no chance of t hem get t i ng near t he hi gh vol t age or any shar p met al edges et c. Your pi ct ur e qual i t y may be a t ad l ower t han i t was bef or e because of t he added st r ay capaci t ance of t he f i l ament wi r i ng bei ng att ached to t he t he ( f or mer l y bad) vi deo si gnal , but hey, somet hi ng i s bet t er t han not hi ng. 11. 7)
Rescui ng a shor t ed CRT
I f t he shor t i s f i l ament - cat hode ( H- K) , you don' t want t o use t he f ol l owi ng appr oach si nce you may bl ow out t he f i l ament i n t he pr ocess. I f t hi s i s t he case, you may be abl e t o f l oat t he f i l ament and l i ve wi t h t he shor t ( see t he sect i on on: Red, gr een, or bl ue f ul l on - f og over pi ct ur e. Short s i n t he CRT t hat ar e bet ween di r ect l y accessi bl e el ect r odes can be deal t wi t h i n a mor e di r ect way t han f or H- K shor t s. At t hi s poi nt you have not hi ng t o l oose. A short ed CRT i s not r eal usef ul .
I f t he shor t i s bet ween t wo di r ect l y accessi bl e el ect r odes l i ke cat hode- gr i d, t hen as a l ast r esor t , you mi ght t r y zappi ng i t wi t h a char ged capaci t or . St ar t wi t h a rel at i vel y smal l capaci t or - say a f ew uF at a coupl e hundr ed vol t s. Check t o see i f t he shor t i s bl own af t er each zap - f ew may be needed. I ncrease t he capaci t ance i f you f el l l ucky but have had l i t t l e success wi t h t he smal l capaci t or . I f t he f aul t i s i nt er mi t t ent , you wi l l , of cour se, need t o cat ch t he CRT wi t h t he socket di sconnect ed and t he shor t s t i l l pr esent . Try some gent l e t appi ng i f necessary. I f you do t hi s wi t h t he char ged capaci t or acr oss t he suspect el ect r ode, you WI LL know when t he shor t occur s! 11. 8)
Br i ght eni ng an ol d CRT
I f per f or mi ng adj ust ment s of t he i nt er nal backgr ound and/ or scr een cont r ol s st i l l r esul t s i n a dar k pi ct ur e even af t er a l ong war mup per i od, t he CRT may si mpl y be near t he end of i t s usef ul l i f e. I n t he ol d days of TVs wi t h shor t l i ved CRTs, t he CRT br i ght ener was a common i t em ( sol d i n ever y cor ner dr ugst or e, i t seemed! ) . You can t he CRT seconds f or t he
t r y a si mi l ar appr oach. - possi bl y qui t e dr amat i or mi nut es) . However , i scr ap heap, i t i s wor t h
CAUTI ON: t hi s may shor t en t he l i f e of cal l y (l i ke i t wi l l bl ow i n a coupl e of f t he moni t or or TV i s ot herwi se dest i ned a t r y.
The appr oach i s si mpl e: you ar e goi ng t o i ncr ease t he vol t age t o t he f i l ament s of t he el ect r on guns maki ng t hem r un hott er . Hopef ul l y, j ust hot t er enough t o i ncr ease t he br i ght ness wi t hout bl owi ng t hem out . Vol t age f or t he CRT f i l ament i s usual l y obt ai ned f r om a coupl e of t ur ns on t he f l yback t r ansf or mer . I t i s usual l y easy t o add an extr a t ur n or t wo whi ch wi l l i ncr ease t he vol t age and t hus t he cur r ent maki ng t he f i l ament s r un hot t er . Thi s wi l l al so shor t en t he CRT l i f e - per haps rather dr ast i cal l y. However , i f t he moni t or was headed f or t he dumpst er anyhow, you have not hi ng t o l os e. Ther e ar e al so commer ci al CRT r ej uvenat or s t hat supposedl y zap t he cat hodes of t he el ect r on guns. A TV r epai r shop may be abl e t o pr ovi de t hi s ser vi c e, t hough i t i s , at bes t , a s hor t t er m f i x. 11. 9)
Bl eedi ng hi ghl i ght s
On ver y br i ght ar eas of t he pi ct ur e, one or mor e col or s may bl eed t o t he r i ght r esul t i ng i n a t r ai l of t hose col or s. The di f f er ence bet ween t hi s pr obl em and t he sect i on: Tr ai l i ng l i nes i n one or mor e col or s i s that i n t hi s case, onl y hi ghl i ght s ar e af f ected. One cause of t hi s i s t hat t he col or gai n, cont r ast , or i nt ensi t y cont r ol s ( what ever t hey ar e cal l ed on your s et ) ar e set t oo hi gh. See t he sect i on on: Col or bal ance. Check the set t i ngs of any br i ght ness l i mi t er cont r ol s as wel l . 11. 10)
Tr ai l i ng l i nes on one or more col or s
The f ol l owi ng i s f r om: ( I an Whi t e ( 100743. 1026@COMPUSERVE. COM) ) .
Check t he power suppl i es t o t he vi deo ci r cui t s as wel l as t he CRT f i l ament ( l ow heat er vol t s can cause t r ai l i ng) . Al so swap t he t he dr i ves bet ween t he r ed and gr een guns ( or whi chever col or i s af f ect ed i n your case) or t he col or out put t r ansi st or s. I f t he same col or i s al ways tr ai l i ng t hen you can be cer t ai n i t i s t he t ube and i t wi l l need r eact i vat i ng or see t he dumpst er . 11. 11)
Pi ct ur e f ades i n and out
I f t he pi ct ur e f aded away on t he or der of 10- 20 seconds ( and i f i t comes back, al so comes up t o f ul l br i ght ness i n same t i me f r ame - possi bl y wi t h t he per suasi on of some car ef ul whacki ng) AND wi t h NO ot her si gni f i cant changes such as si ze, f ocus, et c. , t hen t ake a l ook i n t he back of t he t ube f or t he f i l ament t o be l i t - t he or ange gl ow near t he CRT socket . I f t her e i s none, t hen you pr obabl y have a bad sol der connect i on on t he ci r cui t boar d on t he neck of t he CRT. Look f or f i ne cr acks ar ound pi ns on t hat board. Tr y pr oddi ng i t wi t h an i nsul at i ng st i ck t o see i f t he pi ct ur e comes back. Resol der i f necessar y. I t i s pr obabl y not a bad CRT as t he f i l ament s ar e usual l y wi r ed i n paral l el and al l woul d not go bad at t he same t i me. However , i f onl y a si ngl e col or f ades i n and out , t hen a bad connect i on i nsi de t he CRT i s a di st i nct possi bi l i t y - l ook f or onl y one of t he f i l ament ' s gl ow t o be comi ng and goi ng. Thi s i s pr obabl y not wort h f i xi ng. I f t he pi ct ur e f aded away wi t h ot her sympt oms, t hen t her e i s pr obabl y a f aul t i n t he vi deo ampl i f i er / out put one of i t s power suppl i es st i l l pr obabl y a l oose connect i on i f you ar e abl e to get i t back by whacki ng. 11. 12)
Occasi onal br i ght ness f l ashes
These may l ast onl y a f r act i on of a sc an l i ne or much much l onger . Thi s coul d mean an i nt er mi t t ent f aul t i n a var i et y of pl aces i ncl udi ng t he vi deo ci r cui t r y and SCREEN power suppl y: Br i ght ness ci r cui t r y - SCREEN, mast er backgr ound or i t s power suppl y. Coul d be i n or around f l yback or f ocus/ scr een di vi der. Coul d per haps be i n t he CRT, but pr obabl y l ess l i kel y. Vi deo amp bef or e or at chr oma demodul at or - si nce af t er t hi s poi nt , you woul d most l i kel y get col ored f l ashes si nce onl y one of t he RGB si gnal s woul d l i kel y be ef f ec t ed. I f you get i t f r om al l s our c es , t hen t uner / I F i s r ul ed out . Suppose you j ust have no si gnal t o a di r ect vi deo i nput . What do you get ? I f you st i l l get f l ashes, i t shoul d be r eal easy t o moni t or ei t her t he vi deo out put s or SCREEN suppl y ( wi t h a HV di vi der on your scope) f or noi se. Then t r ace back t o power or noi se sour ce. 11. 13)
Excessi ve br i ght ness and/ or washed out pi ct ur e
Excessi ve br i ght ness/ washed out pi ct ur e i s of t en an i ndi cat i on of a pr obl em wi t h t he SCREEN suppl y t o t he CRT. May be a bad capaci t or or r esi st or di vi der of t en i n t he f l yback t r ansf or mer assembl y or on t he boar d on t he neck of t he CRT.
I f t he excessi ve br i ght ness j ust devel oped over t i me, t hen a si mpl e adj ust ment of t he SCREEN or backgr ound br i ght ness cont r ol s may keep i t ( and you) happy f or a l ong ti me. When good, a t ypi cal val ue woul d be i n t he 200- 600 VDC at t he CRT. The SCREEN ( may be cal l ed mast er br i ght ness or backgr ound) cont r ol shoul d var y t hi s. I t coul d al so be a pr obl em wi t h bi asi ng of t he vi deo out put t r ansi st or s. Ther e may i ndi vi dual cont r ol s f or backgr ound br i ght ness on t he l i t t l e boar d on t he neck of t he CRT. However , we ar e l ooki ng f or a common pr obl em si nce al l col or s ar e wr ong i n t he same way. Fi r st , check f or bad connect i ons/ col d sol der j oi nt s by gent l y pr oddi ng wi t h an i nsul at i ng st i ck. Check vol t ages and bi as l evel s. 11. 14)
Bad f ocus ( f uzzy pi ct ur e)
Focus vol t age on t he CRT i s usual l y i n t he r ange of 2- 8 KV DC and shoul d be cont r ol l abl e over a f ai r l y wi de r ange by t he f ocus pot . The f ocus pot i s usual l y l ocat ed on t he f l yback t r ansf or mer or on an auxi l i ar y PCB near by. The f ocus wi r e usual l y comes f r om t he f l yback or i f t he gener al area or f r om a t er mi nal on a vol t age mul t i pl i er modul e i n some cases. I t i s usual l y a wi r e by i t sel f goi ng t o t he l i t t l e boar d on t he neck of t he CRT. I f a spar k gap ( a l i t t l e 2 t er mi nal devi ce wi t h a 1/ 8 gap i n t he mi ddl e) i s ar ci ng wi t h power on, t hen t he r esi st i ve di vi der has short ed i nsi de t he f l yback, f ocus board, or HV mul t i pl i er - what ever you TV has - and t he t hi s uni t wi l l need t o be r epl aced. Di t t o i f t he SCREEN cont r ol af f ect s f ocus and/ or vi ce- ver sa. Usi ng a sui t abl e vol t met er ( r ange at l east 10KVDC) , you shoul d be abl e t o measur e i t connect ed and di sconnect ed. The gr ound r et ur n wi l l be t he out si de coat i ng of t he CRT whi ch may or may not be t he same as t he met al chassi s part s. I f t he vol t age i s ver y l ow ( l ess t han 2K) and t he pot has l i t t l e ef f ect : When measur ed r i ght of f of t he sour ce di sconnect ed f r om t he CRT ci r cui t , t hen t he pr obl em i s probabl y i n t he f ocus net wor k i n t he f l yback ( or wher ever i t or i gi nat es) . Somet i mes t hese can be di sassembl ed and cl eaned or r epai r ed but usual l y requi r es r epl acement of t he ent i r e f l yback or vol t age mul t i pl i er . When measur ed wi t h t he CRT connect ed but r easonabl e wi t h i t di sconnect ed, t hen check f or a bad capaci t or on t he l i t t l e ci r cui t boar d. The CRT coul d al s o c aus e t hi s but i t i s unl i kel y. 11. 15)
Focus dr i f t wi t h war mup or age
Focus i s cont r ol l ed by a vol t age of 2- 8 KV DC usual l y der i ved f r om t he f l yback t r ansf ormer and i ncl udes some r esi st ors and capaci t ors . One of t hese coul d be changi ng val ue as i t warms up. ( assumi ng not hi ng el se changes si gni f i cant l y as t he uni t warms up. E. g. , t he br i ght ness does not decr ease. )
Focus i s usual l y a separ ate wi r e r unni ng f r om t he f l yback or i t s nei ghbor hood t o t he PCB on t he neck of t he CRT. Look f or component s i n t hi s gener al ar ea. Use ' col d spr ay' t o i sol at e t he one t hat i s dr i f t i ng. I f you have access t o a hi gh vol t age met er , you shoul d be abl e t o see t he vol t age change as t he TV or moni t or war ms up - and when you cool t he f aul t y part . I f i t i s i n t he f l yback, t hen somet i mes t he par t wi t h t he adj ust ment s cl i ps of f and can be r epai r ed or cl eaned. Most of t en, you wi l l need t o r epl ace t he f l yback as a uni t . Focus vol t age i s der i ved f r om a subset of t e hi gh vol t age wi ndi ng on t he f l yback usi ng a resi st i ve vol t age di vi der whi ch i ncl udes t he f ocus pot . These ar e ext r emel y hi gh val ue r esi st or s - 200 M ohm i s common - and so l eakage of any ki nd can r educe or i ncr ease t he f ocus vol t age. Al l ot her t hi ngs bei ng ok - i . e. , t he pi ctur e i s ot her wi se f i ne - I woul d suspect t hi s t ype of f ai l ur e rat her t han t he CRT. I f you have a hi gh vol t age met er , you can measur e t he f ocus vol t age t o det er mi ne i f i t i s bei ng changed by t he f ocus pot and i f i t i s i n t he bal l park (2- 8 KV t ypi cal ) . Somet i mes, t he part of t he f l yback wi t h t he f ocus pot can be snapped of f and cl eaned or par t s r epl aced but usual l y you need t o r epl ace t he whol e uni t . Ther e may a capaci t or or t wo on t he PCB on t he neck of t he CRT t hat coul d have i ncr eased l eakage as wel l t hus r educi ng t he f ocus vol t age. 11. 16)
Bad f ocus and adj ust ment changes br i ght ness
Thi s i s t he cl ass i c sympt om of a shor t bet ween t he f ocus and sc r een suppl i es - pr obabl y i n f ocus/ screen di vi der whi ch i s par t of t he f l yback or t r i pl er . I f you have a hi gh vol t age met er , measur i ng t he f ocus vol t age wi l l show t hat ( 1) i t i s l ow and ( 2) i t i s af f ect ed by the SCREEN cont r ol Si mi l ar l y, t he SCREEN vol t age wi l l be af f ect ed by t he FOCUS cont r ol ( whi ch i s what i s changi ng t he br i ght ness. Ther e i s a sl i ght possi bi l i t y t hat t hi s may be i n t he CRT as wel l . Measur e t he FOCUS and SCREEN vol t age wi t h a hi gh vol t age met er . I f t hey ar e i dent i cal pul l t he pl ug on t he CRT. I f t hey are now t hei r normal val ues, t hen a shor t ed CRT i s a di st i nct possi bi l i t y - see t he secti on: Rescui ng a shor t ed CRT. 11. 17)
Bl ank pi ct ur e, good channel t uni ng and sound
Si nce the t uner and sound ar e ok, hor i zont al def l ect i on whi ch usual l y gener at es power f or most of t he set i s al so worki ng. Does ' bl ank pi ct ur e' means a t ot al l y bl ack scr een wi t h t he br i ght ness and cont r ast cont r ol s havi ng no ef f ect what soever ? Or , i s ther e i s no pi ct ur e but t her e i s a r ast er - l i ght on t he screen? The di r ect i on i n whi ch t r oubl eshooti ng shoul d pr oceed di f f er si gni f i cant l y dependi ng t he answer . Her e ar e some quest i ons: As above, i s t her e any l i ght on t he scr een at any set t i ngs of t he br i ght ness and cont r ast cont r ol s, and/ or when swi t chi ng channel s. Can you see any r ast er scanni ng l i nes? Can you hear t he hi gh pi t ched ( 15735 Hz) of t he hori zont al def l ect i on?
Looki ng i n t he back of t he set , can you see t he gl ow of t he CRT f i l ament ? Do you get t hat st ati c on t he f r ont of t he t ube that woul d i ndi cat e that t her e i s hi gh vol t age? Any cr acki ng or ot her nor mal or abnor mal sounds or smel l s? Possi bl e causes of no rast er : no/ l ow HV, dr i ve t o CRT bad/ shut of f as a r esul t of f aul t el sewher e, bl anki ng as a r esul t of t uner / cont r ol l er mal f unct i on, f i l ament t o CRT not get t i ng power ed. Possi bl e causes of no vi deo: pr obl em i n vi deo I F, vi deo ampl i f i er s, vi deo out put , cut of f due t o ot her f aul t . I t coul d be as si mpl e as a bad connect i on - t r y gent l y pr oddi ng t he boar ds wi t h an i nsul at ed st i ck whi l e wat chi ng t he scr een. Check f or l oose connect ors and r eseat al l i nt er nal connect or s. 11. 18)
Pur pl e bl ob - or wors e
Have you t r i ed demagnet i zi ng i t ? Try power i ng i t of f f or a hal f hour , t hen on. Repeat a coupl e of t i mes. Thi s shoul d act i vat e t he i nt er nal degausser . See the sect i on: Degauss i ng ( demagnet i zi ng) t he CRT. I s t her e any chance t hat someone waved a magnet hear t he t ube? and/ or move any i t ems l i ke monst er speaker s away f r om t he set .
Remove i t
Was your ki d exper i ment i ng wi t h nucl ear expl osi ves - an EMP woul d magnet i ze t he CRT. Near by l i ght eni ng st r i kes may have a si mi l ar ef f ect . I f demagnet i zi ng does not hel p, t hen i t i s possi bl e t hat somet hi ng shi f t ed on t he CRT - t her e are a var i et y of l i t t l e magnet s t hat ar e stuck on at t he t i me of manuf act ur e t o adj ust pur i t y. Ther e are al so servi ce adj ust ment s but i t i s unl i kel y ( t hough not i mpossi bl e) t hat t hese woul d have shi f t ed suddenl y. Thi s may be a t ask f or a ser vi ce shop but you can t r y your hand at i t i f you get t he SAMs Phot of act or ser vi ce manual - don' t at t empt pur i t y adj ust ment s wi t hout one. I f t he set was dr opped, t hen i t i s even possi bl e that t he i nt er nal shadowmask of t he CRT has become di st or t ed and you now have a hundr ed pound paper wei ght . I t i s even possi bl e t hat t hi s i s a ' f eat ur e' compl ement s of t he manuf act ur er . I f cer t ai n component s l i ke t r ansf or mer s and l oudspeaker s ar e of i nf er i or desi gn and/ or ar e l ocat ed t oo cl ose t o t he CRT, t hey coul d have an ef f ect on pur i t y. Even i f you di d not not i ce t he pr obl em when t he set was new, i t mi ght al ways have been margi nal and now a di scol orat i on i s vi si bl e due t o sl i ght changes or movement of component s over t i me. 11. 19)
Col or TV onl y di spl ays one col or
I assume t hat now you have no ot her col or s at al l - no pi ct ur e and no r as t er . L et us s ay i t i s r ed - R. I t i s pr obabl y not t he CRT. Do you have a scope? Check f or t he R, G, and B vi deo si gnal s at t he CRT. You wi l l pr obabl y f i nd no si gnal s f or t he def ecti ve col or s.
Thi s i s al most cer t ai nl y a chr oma ci r cui t pr obl em as any f ai l ur e of t he CRT or a vi deo dr i ver woul d cause i t t o l ose a si ngl e col or - t he ot her t wo woul d be ok. Ther ef or e, i t i s pr obabl y NOT t he CRT or a dr i ver on t he l i t t l e boar d on t he neck of t he CRT. Tr y t ur ni ng up t he SCREEN cont r ol t o see i f you can get a G and B r ast er j ust t o conf i r m t hat t he CRT i s ok. Locat e t he vi deo dr i ve f r om t he mai nboar d f or t he good and a bad col or . I nt er change t hem and see i f t he pr obl em moves. I f so, t hen t her e i s a vi deo si gnal pr obl em. I f not , i t i s on t he l i t t l e CRT boar d. I t coul d be a def ect i ve chr oma I C or somet hi ng el se i n t he chr oma decoder . 11. 20)
Di sappeari ng Red ( or ot her col or )
Pr obl em: I have been gi ven an ol d col our TV. The r ecept i on i s good, but ver y of t en, when t he cont r ast and br i ght ness of t he TV i mage i s l ow ( e. g. when a ni ght scene i s shown) , t he r ed col our sl owl y di sappear s, l eavi ng behi nd t he gr een and bl ue i mage and many r ed l i nes. The r emai ni ng r ed r et r ace ar e t he gi veaway t hat t hi s i s most l i kel y not a CRT pr obl em. ( I f t her e wer e no red l i nes, i t coul d be the f i l ament f or t he r ed gun of t he CRT goi ng on and of f due t o a bad connect i on i nsi de t he CRT bad news. ) How i s a bl ack and whi t e pi ct ur e?
( Tur n down t he col or cont r ol ) .
I f B/ W pi ct ur e i s good, t hen t he pr obl em i s somewher e back i n t he chr oma decoder ci r cui t r y. Check t he vi deo i nput t o t he CRT vi deo dr i ver boar d and si gnal s on t hat boar d. I f B/ W pi ct ur e i s al so bad, t hen you can compare r ed and gr een si gnal s t o det er mi ne where t hey ar e becomi ng di f f er ent . The r ed l i nes i n your descri pt i on sounds l i ke t he r ed vi deo out put ci r cui t i s dr i f t i ng and messi ng up t he backgr ound l evel , bl anki ng, scr een, or ot her set t i ng. Coul d be a capaci t or or ot her component . Chapt er 12) 12. 1)
Tuner and AGC Pr obl ems
No r ecept i on f r om ant enna or cabl e
Make sur e your sour ce i s pr ovi di ng a si gnal and t hat t he cabl e connect ors are good ( cent er pi n not br oken or bent ) . Tr y anot her TV i f possi bl e. Make sur e you sour ce sel ect s wi t ch or mode i s set cor r ect l y. may have acci dent al l y set i t t o di r ect vi deo or AUX i nput .
Someone
Ar e al l bands af f ec t ed? I f s o, t he t uner or I F i s f aul t y. I f t her e i s a l ot of snow, t hen i t i s pr obabl y towar d t he f r ont ( ci r cui t r y wi se) of t he t uner . I f i t i s j ust a bl ack screen, t hen i t coul d be i n t he I F or vi deo ampl i f i er . I f onl y cer t ai n bands ar e bad - channel s 2- 6 f or exampl e, t hen cer t ai n part s of t he t uner ci r cui t r y ar e f aul t y. However , make sur e t he CATV
mode i s set cor r ect l y as t hi s af f ect s r ecept i on on a band- by- band basi s. The pr obl ems may be due t o bad sol der connect i ons of t he t uner shi el ds, connect ors , coi l s, and ot her component s. Try pr oddi ng t he t uner t o see i f you can make t he pr obl em come and go or at l east change. 12. 2)
Pi ct ur e i s over l oaded, washed out , or noi sy
Thi s i ndi cat es an Aut omat i c Gai n Cont r ol ( AGC) pr obl em of t en caused by a dr i ed up capaci t or . You wi l l pr obabl y need a schemat i c t o go much f ur t her . Thi s coul d be a pr obl em i n t he t uner , I F, or vi deo ampl i f i er s. 12. 3)
I nt er f er ence when usi ng VCR RF connect i on
( Some of t hese comment s al so appl y t o use of Laser Di sc pl ayer s, sat el l i t e r ecei ver s, vi deo games, or ot her sour ces wi t h RF modul at or ( Channel 3/ 4) out put s) . Thi s may consi st of pat t er ns or l i nes i n t he pi ct ur e. I f t hi s onl y happens on t he ant enna or cabl e, i t may be a pr obl em wi t h t hese sour ces or t he t uner i n t he VCR r at her t han t he TV. As a t est , t r y t he connect i ng t he TV di r ect l y t o the ant enna or cabl e. I f i t onl y happens on cabl e, t her e may be a ( t emporar y) pr obl em wi t h cabl e t r ansmi ssi on - cont act your cabl e company. I f i t happens on pl ayback of good qual i t y ( commer ci al ) r ecordi ngs, t hen i t coul d be a compat i bi l i t y pr obl em bet ween t he VCR and TV. Make sur e your pat ch cabl e connect i ons ar e secur e and t hat t he cabl es ar e not damaged - i n par t i cul ar t hat t he cent er pi n i s i nt act . Tr y f i ne t uni ng i f your TV has t hi s capabi l i t y. I f t hi s does not hel p, t r y swi t chi ng t he channel 3/ 4 sel ect or on t he VCR t o t he opposi t e posi t i on and t r y t hat channel , somet i mes one wi l l be bet t er t han t he ot her par t i cul ar l y i f one of t hese or an adj acent channel i s act i ve i n your ar ea. I f you have RCA baseband vi deo i nput s on your TV, t r y t hi s connect i on t o t he VCR. These shoul d wor k bet t er i n any case. Conf i r m t hat i t i s not act ual l y a pr obl em wi t h t he VCR - t r y anot her TV i f pos si bl e. I f you j ust changed your component pl acement , t he VCR or TV may be pi cki ng up i nt er f er ence f r om anot her component . Tur n of f ever yt hi ng but t he VCR and TV and see i f t hat i dent i f i es t he cul pr i t . Move t he TV away f r om t he VCR so see i f t hey ar e i nt er f er i ng wi t h each ot her - t he TV may be i nt r oduci ng i nt er f er ence i nt o t he VCR. Occasi onal l y, t he par t i cul ar pat ch cabl e or i t s l engt h may af f ect r ecept i on qual i t y - t r y anot her one. I f none of t hi s hel ps, you VCR' s RF modul at or may be bad or sl i ght l y weak. Al t er nat i vel y, t he t uner i n t he TV may be f aul t y. I f r ecept i on i s gener al l y noi sy on al l sour ces, AGC or RF/ I F al i gnment may need adj ust i ng. However , not al l t uner s are cr eat ed equal . Your TV may si mpl y be maki ng t he best of a margi nal si t uat i on.
A l i ght di mmer on t he same ci r cui t as t he TV may r esul t i n si mi l ar sympt oms. I f you ar e t uni ng up your mot or cycl e ( or aut omobi l e) i n t he same r oom, t hi s may be spar k i gni t i on i nt er f erence. 12. 4)
Mi ssi ng or noi sy channel or bl ock of channel s
I f you ar e unabl e t o recei ve cer t ai n channel s or bl ocks of channel s, t hi s i s a t uner pr obl em - coul d be as si mpl e as bad connect i ons - or even si mpl er : . Fi r st , check t o see t hat t he t uni ng mode i s corr ect - TV, CATV, as t hi s i s t he most common cause of channel s ' di sappeari ng' . TV channel s ar e ass i gned f r equenci es r angi ng f r om 72 t o al most 800 MHz dependi ng on br oadcast or c abl e channel assi gnment . To t une over such a wi de r ange r equi r es spl i t t i ng i t up i nt o var i ous bands even i f t hese ar e not act ual l y def i ned. I f you have a var act or t uned set , t hen you al r eady know about t he Vl , Vh, and U bands whi ch may use separ at e f r ont - end component s. Even moder n quar t z PLL synt hesi zed t uner s need t o al l ocat e ci r cui t r y dependi ng on f r equency r ange. Ther ef or e, i f a bl ock channel s i s not wor ki ng, i t coul d be due t o a f ai l ur e of some component r el at ed t o t hat f r equency r ange. Asi de f r om l ooki ng f or bad connect i ons, r esol der i ng t he shi el ds and connect or pi ns, pr oddi ng, pr essi ng, pr ayi ng, et c. you wi l l need a schemat i c t o have any chance of f i ndi ng such a f aul t . Ther e i s anot her sl i ght possi bi l i t y. Some TVs have a par ent al l ockout capabi l i t y (pr e V- chi p) t o pr event ki ds or ot her unaut hor i zed access t o sel ect ed channel s. The channel sel ect i ons may have been acci dent al l y al t er ed. Check your user manual f or i nst r uct i ons on pr ogr ammi ng t hi s f eat ur e. Even on model s wi t hout t hi s opt i on, t he same i nt er nal ci r cui t r y coul d be pr esent but not nor mal l y accessi bl e. A power sur ge or st r ay cosmi c r ay coul d have put t he set i n a scr ewy mode. Unpl uggi ng power f or a mi nut e or pr obabl y a much l onger t i me mi ght poss i bl y r eset such an anomal y. 12. 5)
Loss of Channel af t er War mup
I f t her e i s a gener al l oss of pi ct ur e and sound but t her e i s l i ght on t he scr een, t hen most l i kel y t he t uner or I F st age i s poopi ng out . Wi t h bot h no sound and no pi ct ur e but a rast er and st at i c, i t i s most l i kel y a pr obl em i n t he t uner , power t o t he t uner , or i t s cont r ol l er ( i f non- knob t ype) . I f i t r ecover s af t er bei ng of f f or a whi l e, t hen you need t o t r y a col d spr ay i n t he t uner / cont r ol l er t o i dent i f y the component t hat i s f ai l i ng. Take appr opr i at e saf et y pr ecaut i ons whi l e wor ki ng i n t her e! I f i t st ays br oken, t hen most l i kel y some component i n t he tuner , i t s cont r ol l er , or i t s power suppl y as f ai l ed. Ther e i s a sl i ght chance t hat i t coul d be a bad sol der connect i on - I have seen t hese i n t he t uner modul es of RCAs on sever al occasi ons ( and many ot her manuf act ur er s - appar ent l y not a sol ved manuf act ur i ng pr obl em even af t er 40+ year s! 12. 6)
Channel t uni ng dr i f t s as set warms up
Thi s may be a sl i ght dr i f t - l i ke someone i s mess i ng wi t h t he f i ne t uni ng or such a subst ant i al change i n t uni ng f r equency t hat t he channel s go by
as t hough you ar e surf i ng. Possi bl e causes depend on t uner t ype: Quar t z t uner ( 10 but t on di r ect access di gi t al synt hesi zer ) - For a sl i ght dr i f t , a component i s pr obabl y changi ng val ue, possi bl y t he crystal i n t he r ef er ence osci l l at or . For gr oss changes - f l i ppi ng t hr ough channel s - i t i s mor e l i kel y to be a di gi t al cont r ol pr obl em t he mi cr ocont r ol l er i s mi sdi r ect i ng t he synt hesi zer t o change f r equency. Var act or t uner ( but t ons but not di r ect channel access) - I f onl y a si ngl e pushbut t on sel ect i on i s t he pr obl em, t he the var act or t uni ng di ode f or t hat but t on i s pr obabl y changi ng capaci t ance. I f al l channel s i n a band ( Vl , Vh, U) ar e havi ng a pr obl em, i t i s mor e l i kel y t o be a dr i f t i ng D/ A or f aul t y AFT ( Aut omat i c Fi ne Tuni ng) ci r cui t or power suppl y. Tur r et or swi t ch t uner ( Knobs) - A component l i ke a capaci t or i s changi ng val ue. You wi l l have t o get i n t her e wi t h a heat gun or col d spr ay and t r ack i t down t he ol d f ashi oned way. At l east , t he pr obl em i s al most cer t ai nl y l ocal i zed t o the tuner box (and possi bl y the cont r ol l er i f appl i cabl e) . As not ed, gr adual sl i ght changes i n tuni ng ar e l i kel y due t o f r equency det er mi ni ng component s dr i f t i ng. Uncont r ol l ed channel sur f i ng i s pr obabl y a l ogi c pr obl em. For t he quar t z t uner , t hi s coul d st i l l be mar gi nal connect i ons causi ng t he mi cr opr ocessor t o mi sdi r ect t he synt hesi zer t o change channel s. For t he l at t er case, par t i cul ar l y, t he cause may sti l l be bad connect i ons r esul t i ng i n l oss of channel memor y and/ or er r at i c behavi or . 12. 7)
Noi se i n pi ct ur e and sound due t o br i ght scene
When a br i ght scene comes, t he scr een f l ashes and t her e i s a l ot of noi se i n t he sound. When a dar k scene comes, t her e i s no f l ash or noi se. Changi ng channel does not hel p. The noi se per si st s even when t he sound i s mut ed. ( The f ol l owi ng i s f r om: Lat t uca@Mi dwest . net ( Sam Lat t uca) ) When t he vi deo det ect or l evel i s adj ust ed t oo hi gh, you wi l l get noi se i n t he sound whi l e screen cont ai ns a l ot of whi t e i nf or mat i on ( i . e. l et t er s) but won' t when onl y dark scenes ar e pr esent . The vi deo l evel adj ust i s usual l y a smal l coi l nor mal l y l ocat ed near t he I F sect i on. Si nce your set i s sever al year s ol d, t hi s woul dn' t be uncommon. I t can be adj ust ed whi l e wat chi ng t he pi ct ur e and l i st eni ng t o t he sound. Chapt er 13) 13. 1)
Audi o Pr obl ems
Pi ct ur e f i ne, no audi o
Fi r st check t hat any mut i ng cont r ol i s not act i vat ed. Thi s mi ght be a but t on on t he r emote or set i t sel f . I f you have a headphone j ack, i t may have di r t y cont act s as pl uggi ng i n a headphone usual l y mut es t he speaker .
I f t he set i s mono or onl y one channel of a st er eo set i s out , t hen check f or bad connect i ons t o t he l oudspeaker . Test t he l oudspeaker by di sconnect i ng one of t he wi r es ( wi t h t he power of f ! ) and measur i ng i t s r esi st ance wi t h an ohmmet er ( i t shoul d be l ess t han 100 ohms - pr obabl y l ess t han 8 ohms) . Or moment ar i l y t ouch a 1. 5 vol t bat t er y t o t he speaker t er mi nal s - you shoul d get a cl i ck or pop f r om t he speaker . Next, t r ace back f r om t he speaker out put t er mi nal s t o t he ci r cui t board and l ook f or bad sol der connect i ons or a l oose or di r t y connect or. I f t hese t est s do not r eveal anyt hi ng, you pr obabl y need a scope ( or audi o si gnal t r acer ) and schemat i c. Or at l east t he par t number of f of t he chi p. I s t he f i nal amp a chi p al so or j ust a t r ansi st or? Have you t est ed t he t r ansi st or ? I f t her e i s l i t t l e or no buzz f r om t he speaker , t hat woul d i ndi cat e a pr obl em f ai r l y near t he out put . I f t he t uner / i f wer e bad, I woul d expect some noi se/ humm pi ckup f r om t he l ow l evel audi o st ages. Get t he par t number of f of t he chi p. I f i t i s i n a socket , check t he cont act s f or cor r osi on or l ooseness. 13. 2)
Weak or di st or t ed audi o
Assumi ng you ar e not at t empt i ng t o pl ay i t at ear shat t er i ng l evel s, t hi s may be due t o an al i gnment pr obl em i n t he I F/ audi o demodul at or, a bad audi o I C or ot her ci r cui t r y, bad connect i on, or a def ect i ve speaker . I f your TV has an ear phone or audi o l i ne out j ack, t r y thi s t o see i f i t i s cl ear . I f so, t hen your probl em i s i n t he f i nal audi o amp or speaker ( s) . I f onl y one channel of a st er eo TV i s af f ect ed, i t i s al most cer t ai nl y t he audi o amp or speaker f or t hat channel . I nt er change connect i on t o t he t wo speakers t emporar i l y and see i f t he pr obl em moves. I f t he pr obl em i s at al l i nt er mi t t ent - t r y gent l y whacki ng t he TV - t hen i t i s l i kel y a bad connecti on - ei t her a col d sol der j oi nt or a di r t y or t i r ed I C s oc ket . The audi o ampl i f i er s i n newer TVs ar e al most al ways I Cs and r epl acement s ar e usual l y r eadi l y avai l abl e. I f t he I C i s i n a socket , r emove t he I C, cl ean t he pi ns and socket cont act s and r ei nst al l i t . Somet i mes, t he cont act s on ol d socket l ose t hei r spr i ngi ness and do not pr ovi de sol i d connect i ons. Such a socket wi l l need t o be r epl aced. I f t he set uses di scret e t r ansi st or s, i t s al so possi bl e f or one of t hese t o become noi sy. I f your TV i s f ai r l y ol d - 10 year s or so - t hi s may be an al i gnment pr obl em r equi r i ng t weaki ng of a coi l i n t he sound I F. See your ser vi ce manual . I t may be possi bl e t o have si mi l ar pr obl ems wi t h newer TVs but t hi s i s r el at i vel y r a r e. 13. 3)
Buzzi ng TV
Do you act ual l y mean buzz - l ow f r equency as i n 60 Hz? Or , do you r eal l y mean hi gh pi t ched whi ne. I f t he l at t er , see t he sect i on: Hi gh pi t ched whi ne or squeal f r om i nsi de TV. I s t he buzz t hr ough t he speaker or f r om t he i nsi de of t he set ?
I f i t i s the speaker , t hen i t i s a desi gn i ssue wi t h t he audi o ci r cui t r y. However , a buzzi ng t hat onl y occur s when t he pi ct ur e has shar pl y def i ned t ext or gr aphi cs, may be an over l oad pr obl em at t he sour ce - some TVs si mpl y handl e i t bet t er t han ot her s. I f i t i s f r om i ns i de t he s et , i t i s i n t he def l ec t i on or power s uppl y. Ther e i s a sl i ght possi bi l i t y t hat t he AC power i n your house has some harmoni c cont ent - t he wavef or m i s not si nusoi dal . Thi s mi ght be t he case i f you t r y t o r un on t he same ci r cui t as an act i ve di mmer or somet hi ng el se wi t h t hyr i st or cont r ol . Pr oxi mi t y t o heavy i ndust r y coul d al so cause t hi s. I n nei t her case can you i nf er t he sever i t y of t hi s annoyance f r om specs. I t i s st r i c t l y a des i gn ( e. g. cos t ) i s sue. The si ze of t he TV i s not a st r ong i ndi cat or of t he sever i t y of t he pr obl em but t her e wi l l be some r el at i onshi p as t he power l evel s are hi gher f or l ar ger s et s . Possi bl y r unni ng on a sl i ght l y di f f er ent l i ne vol t age may change i t but t hat i s not r eal l y an opt i on. You coul d t r y a l i ne condi t i oner ( not j ust sur ge suppr ess or ) whi ch i ncl udes f i l t er i ng. I sus pect i t won' t make must di f f er ence. I f i t i s i n t he audi o c i r c ui t s - f r om t he s peaker s or l i ne out - t hen consi der usi ng a ( Hi Fi ) VCR f or t he t uner wi t h an ext ernal st er eo amp and t he i nt er nal speaker di sabl ed. I f i t i s noi se f r om t he TV, t hen t he best you can do i s audi t i on var i ous TVs ver y car ef ul l y t o f i nd one t hat you ar e sat i sf i ed wi t h. BTW, when I got my new super duper RCA Col or t r ak i n 1980, i t had a si mi l ar annoyi ng buzz - even had a r epai r guy out who behaved as t hough t hi s was t o be expect ed. I di d get used t o i t and am not even awar e of i t t oday - and s t i l l us e t hat s et . 13. 4)
Hi gh pi t ched whi ne or s queal f r om TV wi t h no ot her s ympt oms
Fi r s t , make s ur e i t i s not c omi ng f r om t he l ouds peaker i t s el f . I f i t i s , t hen we ar e l ooki ng at an unusual el ect r oni c i nt er f er ence pr obl em r at her t han si mpl y mechani cal vi br at i on. Ther e ar e sever al par t s i nsi de t he TV t hat can pot ent i al l y make t hi s noi se t he hor i zont al f l yback tr ansf or mer and t o a l esser ext ent , t he def l ect i on yoke woul d be my f i r st candi dat es. I n addi t i on, t r ansf ormers or chokes i n t he swi t chi ng power suppl y i f t hi s i s di st i nct f r om t he hor i zont al def l ec t i on ci r c ui t r y . I don' t know about r et ur ni ng a set t o a stor e t hat doesn' t t ake r ef unds ( I won' t even ask about t hat ! ) but assumi ng t hat t hi s sound l evel i s nor mal f or t he par t i cul ar model her e ar e a coupl e of suggest i ons: You do not want t o coat t he TV as t hi s may i nt er f er e wi t h pr oper cool i ng, but t he i nt er i or of t he ent er t ai nment cent er cabi net coul d be l i ned wi t h a non- f l ammabl e sounds absor bi ng mater i al , per haps acoust i c cei l i ng t i l es. Hopef ul l y, not a l ot of sound ener gy i s comi ng f r om t he f r ont of t he set .
Move t he TV out of a cor ner i f t hat i s wher e i t i s l ocat ed - t he cor ner wi l l f ocus sound energy i nt o t he r oom. Anyt hi ng sof t l i ke car pet i ng, dr apes, et c. wi l l do a good j ob of absor bi ng sound ener gy i n t hi s band. I f you are desperat e and want t o check t he i nsi de of t he set : I t i s possi bl e t o coat t he f l yback t r ansf or mer , but t hi s i s used most l y when t her e a l oose cor e or wi ndi ngs and you ar e get t i ng not onl y t he 15, 735 Hz hor i zont al ( NTSC) but al so var i ous subhar moni cs of t hi s. Thi s i s pr obabl y accept abl e but may i ncr ease t he t emper at ur e of t he f l yback. Usi ng appr opr i at e saf et y pr ecaut i ons, you can t r y pr oddi ng t he var i ous suspect par t s ( f l yback, def l ect i on yoke, ot her t r ansf or mer s) wi t h an i nsul at ed t ool such as a dr y wooden st i ck. Li st en t hr ough a car dboar d t ube t o t r y t o l ocal i zi ng t he sour ce. I f t he sounds changes, you know what par t t o go af t er . Somet i mes a r epl acement f l yback wi l l cur e t he pr obl em unl ess i t i s a desi gn f l aw. You do not want t o r epl ace t he yoke as conver gence and ot her adj ust ment s woul d need t o be per f or med. Ot her t r ansf ormers can be r epl aced. Not e t hat t he def l ect i on f r equency - j ust over 15 KHz f or NTSC and PAL - i s on t he bor der of audi bl e f or adul t s but wi l l l i kel y be l oud t o younger peopl e possi bl y t o t he poi nt of bei ng t er r i bl y annoyi ng - or wor se. I f you ar e over 40 ( men mor e so t han women) , you may not be abl e t o hear t he f undament al at al l ( at l east you can l ook f or war d t o si l ence i n t he f ut ur e! ) . So, even sendi ng t he TV back f or r epai r may be hopel ess i f t he t echni ci an cannot hear what you ar e compl ai ni ng about ! Chapt er 14) 14. 1)
Mi scel l aneous Pr obl ems
Gener al err at i c behavi or
You pr ess VOLUME UP and t he channel changes or a set up menu appear s al l by i t sel f j ust at t he cl i max of your myst er y st or y. Bef or e you br eak out t he scr ewdr i ver ( or 12 pound hammer ) , cover up t he I R r emot e sensor . Some t ypes of el ect r oni c bal l asted f l uor escent l i ght s may conf use t he r emot e cont r ol r ecei ver . Or , someone or somet hi ng may be si t t i ng on t he r emot e hand uni t or i t may be def ect i ve and cont i nuousl y i ss ui ng a bad command! Assumi ng t hi s i s not t he sour ce of t he pr obl em: Check f or bad connect i ons - see i f gent l y whacki ng t he TV makes any di f f er ence or t r i gger s t he er r ant behavi or . Bad connect i ons i n t he power suppl y, syst em cont r ol l er , or t uner , may r esul t i n t hi s sor t of behavi or . See t he sect i on: TV and moni t or manuf act ur i ng qual i t y and col d sol der j oi nt s. Ther e coul d al so be noi sy power , a def ect i ve bad mi cr ocont r ol l er , or EEPROM. 14. 2)
J i t t er i ng or f l i cker i ng due t o pr obl ems wi t h AC power
I f you have el i mi nat ed ot her possi bi l i t i es such as el ect r omagnet i c
i nt er f er ence f r om near by equi pment or a f aul t y vi deo cabl e or pr obl ems wi t h t he vi deo i nput ( e. g. , cabl e or VCR) - t hen noi sy or f l uct uat i ng AC power may be a poss i bi l i t y. However , most moder n TVs usual l y have wel l r egul at ed power suppl i es so t hi s i s l ess common t han i t used t o be. Then agai n, your TV may j ust be over l y sensi t i ve. I t i s al so possi bl e t hat some f aul t i n i t s power suppl y r egul at or has r esul t ed i n i t becomi ng more sensi t i ve t o smal l power f l uct uat i ons t hat ar e unavoi dabl e. One way t o det er mi ne i f t he pr obl em i s l i kel y t o be r el at ed t o AC power i s t o r un t he TV on cl ean power i n t he same l ocat i on connect ed t o t he same vi deo i nput . For exampl e, r unni ng i t on an Uni nt er r upt i bl e Power Sour ce ( UPS) wi t h t he l i ne cor d pul l ed f r om t he wal l socket woul d be an excel l ent t est . The out put of t he UPS' s i nver t or shoul d be f r ee of any power l i ne noi se. I f t he TV' s i mage has now set t l ed down: Lar ge appl i ances l i ke ai r condi t i oner s, r ef r i ger at or , or washi ng machi nes on t he same ci r cui t mi ght cause si gni f i cant power di ps and spi kes as t hey c yc l e. Pl uggi ng a t abl e l amp i nt o t he f l uct uat i ons i n power . What el how your house or apar t ment i s may be suppl yi ng power t o wi del
same out l et may per mi t you t o see any obvi ous se i s on t he same ci r cui t ? Dependi ng on wi r ed, t he same f eed f r om t he ser vi ce panel y separ at ed ar eas.
For some unf at homabl e r eason, your TV may j ust be mor e sensi t i ve t o somet hi ng about t he power f r om t he ci r cui t i n t hat r oom. Ther e may be not hi ng act ual l y wr ong, j ust di f f er ent . Whi l e unl i kel y, a l i ght di mmer on t he same ci r cui t coul d be pr oduci ng l i ne- conduct ed i nt er f er ence. I f you have a mul t i met er , you coul d at l east compar e t he vol t ages bet ween t he l ocat i on wher e i t has pr obl ems and t he one wher e i t i s happy. Per haps, t he TV i s sensi t i ve t o bei ng on a sl i ght l y di f f er ent vol t age. Thi s mi ght onl y be a pr obl em i f some ci r cui t r y i n t he t he TV i s margi nal i n some r espect t o begi n wi t h, however . Ther e coul d be a bad connect i on somewher e on t he ci r cui t . has al umi num wi r i ng, t hi s i s a def i ni t e pos si bi l i t y.
I f your house
Tr y a t abl e l amp si nce i t s br i ght ness shoul d f l uct uat e as wel l . Thi s shoul d be checked out by a compet ent el ect r i ci an as i t r epr esent s a r eal f i r e haz ar d. An el ect r i ci an may be abl e t o pi npoi nt t he cause but many do not have t he t r ai ni ng or exper i ence t o deal wi t h pr obl ems of t hi s sor t . Cer t ai nl y, i f you f i nd any power l i ne f l uct uat i ons not account ed f or by maj or appl i ances, on t he same ci r cui t t hi s shoul d be checked by an el ect r i ci an. 14. 3)
My TV has t he shakes
You t ur n on your TV and 5- 10 seconds l at er , t he di spl ay i s shaki ng or vi br at i ng f or a second or so. I t used t o onl y occur when f i r st t ur ned on, but now, t he pr obl em occur s 3 t i mes i n 30 seconds. Of cour se, many var i at i ons on t hi s gener al t heme ar e possi bl e. Some possi bi l i t i es: Ext er nal i nt er f er ence - di d you change anyt hi ng or move your A/ V set up
r ecent l y?
Do you have a comput er moni t or near by?
Def ect i ve ci r cui t r y i n TV - power suppl y r egul at i on, def l ect i on, or bad i nt er nal connect i ons ar e possi bl e. Def ect i ve vi deo cabl e ( unl i kel y) - wi ggl e t he cabl es t o be see i f you can i nduce t he pr obl em. Not e t hat many of t he sour es of el ect r omagnet i c i nt er f er ence t hat are pr obl ems wi t h comput er moni t or s l i ke t r ansf or mer s and power l i nes wi l l not cause not i ceabl e shaki ng, wi ggl i ng, or j i ggl i ng on a TV because t he power l i ne and ver t i cal scan ar e at al most exact l y t he same f r equency and any such movement woul d be ver y s l ow. 14. 4)
TV was r ai ned on
Was t he set pl ugged i n when t he l eak st ar t ed? Any pi ece of equi pment wi t h r emot e power - on capabi l i t y has some por t i ons l i ve at al l t i mes when pl ugged i n and so t her e may have been damage due t o shor t ci r cui t s et c. Subst ant i al damage coul d be done due t o shor t ci r cui t s. Ot her wi se, you may j ust need t o gi ve i t mor e t i me t o dr y out . I have had devi ces wi t h keypads get t i ng wet t hat r equi r ed mor e t han a week but t hen wer e f i ne. Ther e ar e al l ki nds of pl aces f or wat er t o be t r apped and t ake a l ong t i me t o evapor at e. I f t he set got wet whi l e unpl ugged (i n a l eaky exampl e, or i t has a pul l or cl i ck knob on/ of f t o dr y out - compl et el y. Assumi ng al l vi si bl e r epr esent s a mi ni mum saf e t i me t o wai t . Don' t
at t i c or wet basement ) , f or swi t ch, t hen gi ve i t t i me water i s dr ai ned, a week r ush i t .
Gener al l y, some moi st ur e wi l l not do any per manent damage unl ess t he set was on i n whi ch case you wi l l si mpl y have t o t r oubl eshoot i t t he ol d- f ashi oned way - one pr obl em at a t i me. 14. 5)
TV was dr opped
You have pr obabl y seen t he TV adver t i sement s - I don' t r ecal l what t hey wer e f or - wher e a l at e model TV i s dr opped out a many st or y wi ndow on a bunj i e cor d t o r ebound once undamaged and wi t hout hi t t i ng a baby i n a st r ol l er but t hen smash t o smi t hereens on t he si dewal k once t he st r ol l er had moved. Needl ess t o say, t hi s i s gener al l y not a r ecommended way t o t r eat a TV set ! However , mi shaps do happen. Assumi ng i t sur vi ved most l y i nt act - t he CRT di dn' t i mpl ode, you coul d st i l l have a var i et y of pr obl ems. I mmedi at el y unpl ug t he set ! I f you t ake i t i n f or s er vi ce, t he est i mat e you get may make t he nat i onal debt l ook l i ke pocket change i n compari son. At t empt i ng t o r epai r anyt hi ng t hat has been dr opped i s a ver y uncer t ai n chal l enge - and si nce t i me i s money f or a pr of essi onal , spendi ng an unknown amount of t i me on a si ngl e r epai r i s ver y r i sky. Ther e i s no har m i s get t i ng an est i mat e ( t hough many shops char ge f or j ust agr eei ng t hat what you ar e hol di ng was once a - say - a TV, or was i t a f i sht ank?) Thi s doesn' t mean you shoul d not t ackl e i t your sel f .
Ther e may be
not hi ng wr ong or ver y mi nor pr obl ems t hat can easi l y be r emedi ed. f ol l owi ng ar e l i kel y pos si bi l i t i es :
The
Cr acked ci r cui t boar ds. These can be r epai r ed si nce TVs usual l y have f ai r l y wi de open si ngl e or t wo si ded boar ds. Br oken ci r cui t component s.
These wi l l need t o be r epl aced.
Br oken sol der connect i ons par t i cul arl y t o l ar ge heavy component s on si ngl e si ded boar ds. Ref l ow t he sol der . I f t he t r ace i s cracked or l i f t ed, r epai r as i n ( 1) . Br oken mount i ng br acket s. These ar e usual l y made of cheap pl ast i c and of t en don' t sur vi ve ver y wel l . Be cr eat i ve. Obt ai ni ng an exact r epl acement i s pr obabl y not wor t h t he t r oubl e and expense. Component s knocked out of l i ne on t he CRT envel ope or neck - def l ect i on yoke, pur i t y magnet s, conver gence magnet s and coi l s, geomet r y cor r ect i on magnet s. These wi l l need t o be r eat t ached and/ or r eal i gned. Some CRTs use l i t t l e magnet s gl ued t o t he f unnel port i on of t he CRT envel ope. I f any of t hese have come l oose, i t coul d be qui t e a t r eat t o f i gur e out wher e t hey went and i n what ori ent at i on. I nt er nal damage t o t he CRT - popped or di st or t ed shadowmask, mi sal i gned el ect r on guns. Unf ort unat el y, you wi l l pr obabl y have no way of i dent i f yi ng t hese si nce you cannot see i nsi de t he CRT. They wi l l not be appar ent unt i l al l ot her f aul t s have been r emedi ed and t he TV set i s compl et el y r eal i gned. At t hat poi nt , extr emel y sever e pur i t y or conver gence pr obl ems t hat do not r espond t o t he nor mal adj ust ment pr ocedur e woul d be one i ndi cat i on of i nt er nal damage. Gi ve t he TV a ni c e f uner al . I f you s t i l l want t o t ac kl e a r es t o r at i on: As not ed, unpl ug t he TV even i f i t l ooks f i ne. Unt i l you do a t hor ough i nt er nal i nspect i on, t her e i s no t el l i ng what may have been knocked out of whack or br oken. El ect r i cal part s may be short i ng due t o a br oken ci r cui t boar d or one t hat has j ust popped f r ee. Don' t be t empt ed t o appl y power even i f t her e ar e no obvi ous si gns of damage - t ur ni ng i t on may bl ow somet hi ng due t o a shor t i ng ci r cui t board. I f i t i s a por t abl e, r emove t he bat t er i es. Then, i nspect t he ext er i or f or cr acki ng, chi ppi ng, or dent s. I n addi t i on t o i dent i f yi ng cosmet i c pr obl ems, t hi s wi l l hel p t o l ocat e possi bl e ar eas t o check f or i nt er nal damage once t he cover s ar e r emoved. Next, r emove t he cover . Conf i r m t hat t he mai n f i l t er capaci t or s ar e f ul l y di scharged bef ore t ouchi ng anyt hi ng. Check f or mechani cal pr obl ems l i ke a bent or def or med br acket s, cr acked pl asti c par t s, and anyt hi ng that may have shi f t ed posi t i on or j umped f r om i t s mount i ngs. I nspect f or l oose par t s or pi eces of par t s - save t hem al l as some cri t i cal magnet s, f or exampl e, ar e j ust gl ued t o t he CRT and may have popped of f . Car ef ul l y st r ai ght en any bent met al par t s. Repl ace part s t hat wer e knocked l oose, gl ue and possi bl y rei nf or ce cr acked or br oken pl asti c. Pl ast i cs, i n par t i cul ar , ar e t r oubl esome because most gl ues - even pl ast i c cement - do not wor k ver y wel l . Usi ng a spl i nt ( medi cal t er m) or si st er i ng ( const r uct i on t er m) t o rei nf or ce a br oken pl ast i c par t i s of t en a good
i dea. Use mul t i pl e l ayer s of Duco Cement or cl ear wi ndshi el d seal er and sc r ews ( sheet met al or machi ne sc r ews may be best dependi ng on t he t hi ckness and t ype of pl ast i c) . Wood gl ue and Epoxy do not wor k wel l on pl ast i c. Some br ands of super gl ue, PVC pi pe cement , or pl ast i c hobby cement may wor k dependi ng on t he t ype of pl ast i c. I nspect f or any br oken el ect r oni c component s - t hese wi l l need t o be repl aced. Check f or bl own f uses - t he i ni t i al i mpact may have shor t ed somet hi ng moment ar i l y whi ch t hen bl ew a f use. Ther e i s al ways a r i sk t hat t he i ni t i al i mpact has al r eady f r i ed el ect r oni c par t s as a r esul t of a moment ary shor t or f r om br oken ci r cui t t r aces and t her e wi l l st i l l be pr obl ems even af t er r epai r i ng t he vi si bl e damage and/ or r epl aci ng t he br oken component s. Thi s i s most l i kel y i f t he set was act ual l y on but most moder n TVs have some ci r cui t r y ener gi zed at al l t i mes. Exami ne t he ci r cui t boar ds f or any vi si bl e br eaks or cr acks. These wi l l be especi al l y l i kel y at t he corner s wher e t he st r ess may have been gr eat est . I f you f i nd ANY cracks, no mat t er how smal l i n t he ci r cui t boar d, you wi l l need t o car ef ul l y i nspect t o det er mi ne i f any ci r cui t t r aces r un acr oss these cr acks. I f t hey do, t hen t her e ar e cer t ai nl y br eaks i n t he ci r cui t r y whi ch wi l l need t o be r epai r ed. Ci r cui t boar ds i n consumer equi pment ar e al most never mor e t han t wo l ayer s so r epai r i s possi bl e but i f any subst ant i al number of t r aces ar e br oken, i t wi l l t ake t i me and pat i ence. Do not j ust r un over t hem wi t h sol der as t hi s wi l l not l ast . Use a f i ne t i pped l ow wat t age sol der i ng i r on and r un #22- 26 gauge i nsul at ed wi r es bet ween conveni ent endpoi nt s - t hese don' t need t o be di r ect l y on ei t her si de of t he br eak. Doubl e check each connect i on af t er sol der i ng f or cor r ect wi r i ng and t hat t her e are no shor t s bef or e pr oceedi ng t o t he next . I f t he ci r cui t boar d i s beyond hope or you do not f eel you woul d be abl e t o r epai r i t i n f i ni t e t i me, r epl acement s may be avai l abl e but t hei r cost i s l i kel y t o be mor e t han t he equi pment i s wort h. Locat i ng a j unk uni t of t he same model t o canni bal i ze f or part s may be a more r eal i st i c opt i on. Degauss t he set as any i mpact may magnet i ze t he CRT. wor k but a manual degaussi ng i s best .
Power cycl i ng may
Once al l vi si bl e damage has been r epai r ed and br oken par t s have been r epl aced, power i t up and see what happens. Be pr epar ed t o pul l t he pl ug i f t her e are ser i ous pr obl ems ( bi l l owi ng smoke or f i r ewor ks woul d qual i f y) . Per f or m any pur i t y, conver gence, or ot her r eal i gnment as needed. Then pr oceed t o addr ess any r emai ni ng pr obl ems one at a t i me. 14. 6)
Set up menus wi l l not go away or hi er ogl yphi cs on scr een
Bot h t hese pr obl ems coul d be caused by a f aul t y mi cr ocont r ol l er or i t s associ at ed ci r cui t r y. However , bad connect i ons i n t he vi ci ni t y of t he cont r ol l er l ogi c coul d al so be at f aul t . Unl ess you see somet hi ng obvi ous, you wi l l need schemat i cs. 14. 7)
Set up Adj ust ment s Lost
Many moder n TVs have RAM, somewhat l i ke t he CMOS SETUP memor y i n your PC, t hat st or e al l f act ory adj ust ment s. When power i s l ost , t her e i s power
sur ge, l i have put i s a way down and and t hen
ght eni ng st r i ke near by, nucl ear det onat i on or EMP, i t may bad i nf ormat i on i nt o t he r am and t hr own i t out of adj ust ment . Ther e t o get i nt o t he ser vi ce mode ( depr ess and hol d a secr et but t on t ur n set on, speci al combi nat i on of but t ons on t he r emot e, et c. ) use t he r emot e t o r ei ni t i al i ze and adj ust t he pr obl ems out .
HOWEVER, I F YOU DON' T KNOW WHAT YOU DOI NG YOU COULD GI VE YOURSEL F WORSE PROBLEMS. YOU COULD EVEN BLOW THI NGS OUT WI TH SOME SETS! The SAMS Phot of act manual descr i bes t hi s pr ocess - you may be abl e t o get Phot of act s f r om a l ocal l i br ar y, or you can buy them f r om Radi o Shack or a pl ace l i ke MCM El ectr oni cs or an el ectr oni cs di st r i but or . Exampl e: Sony wi t h ver t i cal def l ect i on pr obl ems af t er power f ai l ur e: The f ol l owi ng i s f r om ( Rob myer s, myer 3812@nova. gmi . edu) . I t hi nk, at l east on a KV- 20EXR10, you hol d down t he secr et but t on whi l e t ur ni ng on t he set . An on scr een menu appear s, and t he numer i c keys make adj ust ment s and sel ect t he adj ust ment s t o make. I t hi nk you use 1/ 3 and 4/ 6 or 4/ 6 and 7/ 9 t o do t hi s. The secr et but t on i s a smal l bl ack r ecess i n t he vi deo j ack/ ant enna panel . The adj ust ment s you may need t o make ar e ver t i cal l i near i t y and pi ncushi oni ng. I st r ongl y suggest you get t he SAMS manual bef or e you st ar t maki ng changes. I f i t i s not an adj ust ment pr obl em you pr obabl y have a bad part i n t he ver t i cal power suppl y or out put ( per haps $150 or l ess t o get r epai r ed???) Once agai n, t r y not t o make any unnecess ar y changes and document ever y change you make! ! ! That way you can go back i f you do anyt hi ng wr ong ( hopef ul l y) . I t hi nk t he SAMS manual al so t el l s you how t o r est or e f act ory sett i ngs. 14. 8)
TV doesn' t wor k af t er bei ng i n st orage
So t he TV you car ef ul l y st uf f ed i n a cor ner of t he gar ages i s now t ot al l y dead. You swear i t was wor ki ng per f ect l y a year ago. Assumi ng t her e was absol ut el y no act i on when you t ur ned i t on, t hi s has al l t he cl assi c sympt oms of a bad connect i on. These coul d be col d/ cr acked sol der j oi nt s at l ar ge component s l i ke t r ansf or mer s, power r esi st or s, or connect ors and connect ors t hat need t o be cl eaned or r eseat ed. By ' no act i on' I mean not even a t weet , bl eep, or cr ackl e f r om anyt hi ng. To nar r ow i t down f ur t her , i f car ef ul pr oddi ng wi t h a wel l i nsul at ed st i ck does not i nduce t he set t o come on, check t he f ol l owi ng: Locat e t he hor i zont al out put t r ansi st or . I t wi l l be i n a TO3 met al ( most l i kel y on an ol der set ) or TOP3 pl ast i c package on a heat si nk. Wi t h power of f , measur e col l ect or t o emi t t er wi t h an ohmmet er - i n at l east one di r ect i on i t shoul d be f ai r l y hi gh - 1K or mor e. Then cl i p a vol t met er on t he 250 V DC or hi gher scal e acr oss C- E and pl ug i n and t ur n on t he set . Make sur e i t i s wel l i nsul at ed. I f t he pr obl em i s i n t he l ow vol t age ( l i ne) power suppl y, t her e wi l l be no subst ant i al vol t age acr oss C- E. You shoul d be abl e t o t r ace f r om t he power l i ne f or war d t o f i nd t he bad par t t hough a schemati c wi l l hel p gr eat l y.
I f t he pr o bl em i s i n t he s t ar t up c i r c ui t or hor i z ont al os ci l l at or / dr i ver , t hen t her e wi l l be somet hi ng on t he or der of 100- 160 V acr oss C- E. I n t hi s case, a schemat i c may be essent i al . NOTE: don' t assume t hat t he met al par t s of t he chassi s ar e gr ound - t hey may be f l oati ng at some l i ne pot ent i al . Ther e i s al so a sl i ght chance t hat t her e i s a l ow vol t age r egul at or i n addi t i on t o t he hor i zont al out put , so don' t get t hem conf used. The hor i zont al out put t r ansi st or wi l l be near t he f l yback tr ansf or mer and yoke connect or . 14. 9)
Ol der TVs wi t h mul t i pl e i nt er mi t t ent pr obl ems
I f t he set i s say, a GE, wi t h a manuf act ur i ng dat e ar ound 1980, i t i s possi bl e you have one of t hose ci r cui t boar ds best descr i bed as bad sol der j oi nt s hel d t oget her wi t h a l i t t l e copper . I n t hi s case, pr oddi ng may get t he set st art ed. The ci r cui t boar ds i n t hese set s were doubl e si ded usi ng what wer e cal l ed ' r i vl et s' f or vi as. The r i vl et s wer e r el at i vel y massi ve l i t er al l y l i t t l e copper r i vet s - and t hey wer e not adequat el y heat ed dur i ng assembl y so t here were bucket l oads of col d sol der j oi nt s t hat showed up dur i ng mi ddl e age. I r epai r ed one of t hese by l i t er al l y r esol der i ng t op and bot t om of ever y one of t he dar n t hi ngs wi t h a hi gh wat t age i r on. 14. 10)
TV has bur ni ng smel l
Ass umi ng t her e ar e no ot her sympt oms: I f t hi s appears af t er ext ended oper at i on - an hour or more - i t may j ust be a bui l d up of dust , di r t , and gr i me over t he year s. Af t er under st andi ng t he saf et y i nf o, some car ef ul vacuumi ng i nsi de may hel p. J ust don' t be t empt ed t o t ur n any scr ews or adj ust ment s! Dust i s at t r act ed t o the hi gh vol t age sect i on i n par t i cul ar - even t he f r ont f acepl at e of t he CRT col l ect s a l ot and shoul d be wi ped wi t h a damp cl ot h f r om t i me t o t i me. I f t he sympt oms devel op qui ckl y - i n a f ew mi nut es or l ess, t hen t her e coul d st i l l be a dust pr obl em - a power r esi st or may be heat i ng a wad of i t but ot her possi bi l i t i es need t o be consi der ed. I f not dust , t hen pr obabl y i n t he power suppl y but r eal i ze t hat TVs don' t have a ni ce met al case l abel ed ' power suppl y' . I t i s j ust a bunch of st uf f scat t er ed around t he mai n boar d. Wi t hout i dent i f yi ng t he par t t hat i s heat i ng, a di agnosi s i s t ough especi al l y i f t he set r eal l y does wor k f i ne other wi se. However , i f a ser i es regul ator wer e f aul t y and put t i ng out t oo much vol t age, t he set coul d appear t o wor k pr oper l y but i n f act have excessi ve power di ssi pat i on i n cer t ai n component s. I f cl eani ng t he dust does not sol ve t he pr obl em, you wi l l pr obabl y need a schemat i c t o i dent i f y t he cor r ect vol t ages. 14. 11)
Revi val of dead or t i r ed r emot e cont r ol uni t s
Ther e ar e t wo t ypes of pr obl ems wi t h hand hel d r emot e cont r ol s: t hey have l egs of t hei r own and t hey get abused or f or got t en. I cannot hel p you wi t h wal ki ng r emot es.
Wher e r esponse i s i nt er mi t t ent or t he r el i abl e oper at i ng di st ance i s r educed, f i r st check t he bat t er i es and bat t er y cont act s. I f some but t ons are i nt er mi t t ent or dead, t han t he most l i kel y cause i s di r t y or wor n cont act s under t he rubber but t ons or on the ci r cui t boar d. I f t here i s no r esponse t o any f unct i ons by t he TV or VCR, ver i f y t hat any mode swi t ches ar e set cor r ect l y ( on bot h t he r emot e and t he TV or VCR) . Unpl ug t he TV or VCR f or 30 seconds ( not j ust power of f , unpl ug) . Thi s somet i mes r eset s a mi cr ocont r ol l er t hat may have been conf used by a power sur ge. Conf i r m t hat t he r emot e has not acci dent al l y been set t o an i ncor r ect mode ( VCR i nst ead of TV, f or exampl e) . I f i t a uni ver sal t ype, i t may have l ost i t s pr ogr ammi ng - r eset i t . Make sure you are usi ng t he pr oper r emot e i f have mul t i pl e si mi l ar model s. Test t he r emot e wi t h an I R det ect or . An I R det ect or car d can be pur chased f or about $6. Al t er nat i vel y, bui l d t he ci r cui t at t he end of t hi s document . I f t he r emot e i s put t i ng out an I R si gnal , t hen t he r emot e or t he TV or VCR may have f orgot t en i t s set t i ngs or t he pr obl em may be i n t he TV or VCR and not t he hand uni t . The f ol l owi ng i s j ust a summar y - more det ai l ed i nf or mat i on i s avai l abl e i n t he compani on document : Not es on t he Repai r of Hand Hel d Remot e Cont r ol s. Pr obl ems wi t h r emot e hand uni t s: Al l except ( 1) and ( 2) r equi r e di sassembl y - t her e may be a scr ew or t wo and t hen t he case wi l l si mpl y ' crack' i n hal f by gent l y pr yi ng wi t h a kni f e or scr ewdr i ver . Look f or hi dden snap i nt er l ocks. Dead bat t er i es - sol ut i on obvi ous. Cor r oded bat t er y cont act s, Thor oughl y r emove chemi cal deposi t s. Cl ean cont act s wi t h penci l er aser and/ or sandpaper or nai l f i l e. Br oken connect i ons of t en bet ween bat t ery cont act s and ci r cui t boar d, possi bl y on t he ci r cui t boar d - r esol der . Bad r esonat or or cr ystal - r epl ace, but di agnosi ng t hi s wi t hout an osci l l oscope may be t ough. Br oken connect i ons on r esonat or l egs ar e common. Di r t / spi l l s/ gunk pr event i ng keys f r om oper at i ng r el i abl y. Di sassembl e and wash r ubber membr ane and ci r cui t boar d wi t h wat er and mi l d det er gent and/ or t hen al cohol - dr y compl et el y. Wor n or cor r oded cont act pads on ci r cui t boar d. Cl ean and t hen use conduct i ve Epoxy or pai nt or met al f oi l t o restor e. Worn or di r t y pads on r ubber keypad. pai nt or met al f oi l t o r es t o r e.
Cl ean.
I f wor n, use conduct i ve
Cr acked ci r cui t boar d - can usual l y be repai r ed as t hese ar e usual l y si ngl e si ded wi t h bi g t r aces. Scr ape of f i nsul ati ng coat i ng and j umper br eaks wi t h f i ne wi r e and sol der . Bad LED. I f I R t est er shows no out put , r emove LED and power i t f r om a 9V bat t er y i n ser i es wi t h a 500 ohm r esi st or . I f sti l l no out put , r epl ace wi t h r eadi l y avai l abl e hi gh power I R LED. Ot herwi se, check
dr i ver ci r c ui t s . Bad I C - i f i t i s a cus t om chi p, f or get i t ! i s us ual l y qui t e unl i kel y.
Fai l ur e of t he I C
( The f ol l owi ng i s f r om Duane P Mant i ck: ) An awf ul l ot of I R r emot es use I C' s f r om t he same or si mi l ar ser i es. A common ser i es comes f r om NEC and i s t he uPD1986C whi ch, i nci dent al l y i s cal l ed out i n t he NTE r epl acement s book as an NTE1758. A l ot of t hese chi ps ar e cheap and not t oo di f f i cul t t o f i nd, and ar e made i n easy- t o- wor k- wi t h 14 or 16 pi n DI P packages. Unl ess you have no sol der i ng or des ol der i ng s ki l l s , r epl ac ement i s n' t di f f i c ul t . Ther e ar e a l ar ge var i et y of uni ver sal r emot es avai l abl e f r om $10- $100. For gener al TV/ VCR/ cabl e use, t he $10 var i et y ar e f i ne. However , t he pr epr ogr ammed var i et y wi l l not pr ovi de speci al f unct i ons l i ke pr ogr ammi ng of a TV or VCR. Don' t even t hi nk about goi ng t o t he or i gi nal manuf act ur er - t hey wi l l charge an arm and a l eg ( or more) . However , pl aces l i ke MCM El ect r oni cs do st ock a var i et y of or i gi nal r emot es - pr i ces r ange f r om $9 - $143 ( Wow $143, f or j ust a st upi d r emot e! I t doesn' t even have hi gh def i ni t i on sound or anyt hi ng exot i c) . The aver age pr i ce i s ar ound $40. 14. 12)
Loudspeaker s and TVs
Loudspeaker s i ncorpor at e power f ul magnet s - t he l arger t he speaker , t he l ar ger t he magnet . However , anyone who goes bal l i st i c when t he ment i on i s made of a l oudspeaker near a TV or moni t or , shoul d t ake t hei r Val l i um. The f r i nge f i el ds out si de t he speaker box wi l l not be t hat gr eat . They may af f ect t he pi ct ur e perhaps t o t he poi nt of r equi r i ng degauss. The nor mal degauss act i vat ed at power - on wi l l usual l y cl ear up any col or pur i t y pr obl ems ( ass umi ng t he l oudspeaker s have been moved away) . At wor st , manual degauss wi l l be needed. The CRT wi l l not be damaged. The maxi mum f i el d - i naccessi bl e at t he voi ce coi l - i s qui t e st r ong. However , even f or non- shi el ded l oudspeaker s, t he magnet i c f i el d decays r api dl y wi t h di st ance especi al l y si nce t he cor e st r uct ur e i s desi gned t o concent r ate as much of t he f i el d as possi bl e i n t he gap wher e t he voi ce coi l t r avel s. However , keepi ng speaker s away f r om CRTs i s a good i dea. Now, you r eal l y shoul d keep your super conduct i ng magnet i c r esonance i mager magnet at l east i n t he next r oom. . . . . 14. 13)
Shoul d I r epl ace al l t he el ectr ol yt i c capaci t or s i f I f i nd a bad one?
When a bad capaci t or i s f ound i n a TV, t he quest i on of cour se ar i ses as t o the l i kel i hood of ot her capaci t or s goi ng bad i n shor t or der . I t mi ght be wort h checki ng ( ot her ) caps i n t he power suppl y or hot ( t emper at ur e) ar eas but you coul d spend you whol e l i f e r epl aci ng ALL t he el ect r ol yt i cs i n your ol der equi pment ! Al ways conf i r m t he cust omer ' s compl ai nt s f i r st ! ! Then ver i f y t hat ever yt hi ng el se works or you wi l l never know i f your ef f ort s have af f ect ed somet hi ng unr el at ed. ( Or i gi nal r equest f r om r oger j @apex. com) :
A sweet l i t t l e ol d l ady has duped me i nt o repai r i ng her ol d G. E. 13 col or TV. Want ed me f i x bad vol ume pot . . . . . oh i t has such a good pi ct ur e. . . she says. St upi dl y w/ o even t ur ni ng i t on, ( bi g mi st ake) I begi n t o open t he set . Af t er 15- 20 mi n. of t r avai l , I di scover t hat a pr evi ous r epai r man has gl ued t he case shut ! Now w/ set open, I t ur n poor conver gence. But I t r yi ng t o open i t up. Al wi ht a f ew caps) . Thi s year s.
i t on and t hi s pi ct ur e i s LOUSY. Bad col or, and ver y don' t know i f I ' m t o bl ame f or bangi ng i t ar ound so, no hor i zont al or ver t i cal hol d. ( f i xed t hat t hi ng has pr obabl y been si t t i ng around f or a f ew
Wel l , you cer t ai nl y di d not ki l l t he caps. Anyt hi ng t hat si t s f or a f ew years - pr obabl y i n a damp unheat ed at t i c - i s suspect . Di d you f i nd t he adj ust ment s on t he yoke assembl y t i ght ? I f so, you pr obabl y di d not move anyt hi ng ver y much ei t her . She may r emember t he good pi ct ur e i t pr oduced bef ore bei ng st uf f ed away i n t he at t i c. Anyway af t er goi ng t hr ough al l t he adj ust ment s, t he conver gence at t he si des i s st i l l bad and t he hor i zont al si ze i s a tad i nsuf f i ci ent ( w/ no adj ust ment avai l abl e) Coul d be t hat t he conver gence ( i ncl udi ng pi ncushi on) ci r cui t s ar e st i l l f aul t y - not j ust mi sadj ust ed. Ot her t hi ngs t hat can ef f ect hor i zont al si ze whi l e st i l l gi vi ng you a compl et e pi ct ur e: Vol t age t o hor i zont al out put t r ansi st or l ow. I s ther e a vol t age r egul at or i n your set ? The one I have has none. I assume your l i ne vol t age i s ok. I ncr eased r esi st ance or i nduct ance of t he yoke wi ndi ngs. For al l you know, t he yoke may have been r epl aced wi t h t he wr ong par t . Yoke i mpr oper l y posi t i oned on t ube neck. Excessi ve hi gh Vol t age.
Thi s i s usual l y not adj ust abl e.
I bet t he t hi ng hasn' t worked pr oper l y i n 10 year s. 14. 14)
Phant om spot or bl ob on CRT af t er set i s shut of f
Why i s t her e a spl ot ch of col ored l i ght at t he cent er of t he CRT af t er I ki l l power t o my TV? Why does t hi s not happen i f t he pl ug i s pul l ed i nst ead? I t seems t o l ast f or hour s ( wel l maybe mi nut es at l east ) . Thi s pr obl em sounds l i ke f i el d emi ssi on f r om t he CRT cat hode f or one or mor e guns. Even wi t h t he f i l ament of f , t her e may be some el ect r on emi ssi on f r om t he col d cat hode due to t he st r ong hi gh vol t age ( HV) el ect r i c f i el ds i n t he el ect r on gun. I do not know how l i kel y t hi s i s or why t hi s i s so. When t ur ned of f wi t h t he r emot e or power but t on, you ar e not act ual l y ki l l i ng AC power but ar e pr obabl y swi t chi ng of f t he def l ect i on and si gnal ci r cui t s. Thi s l eaves t he HV t o decay over a f ew mi nut es as i t i s dr ai ned by t he cur r ent needed t o f eed t he phant om spot or bl ob.
When you pul l t he pl ug, however , you are ki l l i ng AC i nput and al l t he vol t ages decay toget her and i n par t i cul ar , t he vi deo si gnal i s st i l l pr esent f or l ong enough t o keep t he br i ght ness up and dr ai n t he HV qui ckl y. A pr oper desi gn ( who knows, your s may si mpl y have been br oken f r om day 1) woul d ensur e t hat t he HV i s dr ai ned qui ckl y or t hat t he ot her bi as vol t ages on t he CRT ar e cl amped t o val ues t hat woul d bl ank t he CRT once t he set i s of f . I f t he pr obl em devel oped suddenl y, t hen t hi s ci r cui t r y may have f ai l ed. On t he ot her hand, i f i t has been gr adual l y get t i ng mor e pr onounced, t hen t he charact er i st i cs of t he CRT or ot her ci r cui t r y may have changed wi t h age. I t may not be wor t h doi ng anyt hi ng t o ' f i x' t hi s unl ess t he spl ot ch i s so br i ght ( mor e so t han nor mal vi deo and f or an ext ended t i me) t hat CRT phosphor damage coul d r esul t . On t he ot her hand, I t may pr ovi de f or some i nt er est i ng conver sat i on at your next part y. 14. 15)
Di sposi ng of dead TVs ( CRTs and char ged HV capaci t or s)
I don' t know what t he l aw says, but f or saf et y, her e i s my r ecommendat i on: Tr eat t he CRT wi t h r espect - t he i mpl osi on hazar d shoul d not be mi ni mi zed. A l ar ge CRT wi l l have over 10 t ons of ai r pr essur e at t empt i ng t o cr ush i t . Wear eye pr ot ect i on whenever deal i ng wi t h t he CRT. Handl e t he CRT by t he f r ont - not t he neck or t hi n f unnel shaped envel ope. Don' t j ust t oss i t i n t he gar bage - i t i s a si gni f i cant hazard. The vacuum can be saf el y r el eased ( l et out ? what does one do wi t h a vacuum?) wi t hout spect acul ar ef f ect s by br eaki ng t he gl ass seal i n t he cent er of t he CRT socket ( may be hi dden by t he i ndexi ng pl ast i c of t he socket ) . Cover t he ent i r e CRT wi t h a heavy bl anket when doi ng t hi s f or addi t i onal pr ot ect i on. Once t he vacuum i s gone, i t i s j ust a bi g gl ass bot t l e t hough t here may be some moder at el y hazar dous mat er i al s i n t he phosphor coat i ngs and of cour se, t he gl ass and shadowmask wi l l have many shar p edges i f i t i s br oken. I n addi t i on, t her e coul d be a ni ce sur pr i se awai t i ng anyone di sconnect i ng t he HV wi r e - t hat CRT capaci t ance can hol d a char ge f or qui t e a whi l e. Si nce i t i s bei ng scr apped, a scr ewdr i ver under t he suct i on cap HV connect or shoul d suf f i ce. The mai n power suppl y f i l t er caps shoul d have di schar ged on t hei r own af t er any r easonabl e l engt h of t i me ( measur ed i n t er ms of mi nut es, not days or years) . Of cour se ar ound her e, TVs are j ust t ossed i nt act whi ch i s f or t unat e f or scavenger s l i ke me who woul d not be happy at al l wi t h pr e- saf ed TVs! 15. 1)
An i nf or mal hi st or y of X- r ay pr ot ect i on
( The f ol l owi ng i s f r om: Mar t y) . Most of t he ol d t ube t ype col or TV set s used a shunt HV r egul at or t ube, usual l y a 6BK4. I f i t f ai l ed, or some component i n t he HV ci r cui t f ai l ed, t he hi gh vol t age, nor mal l y 25KV, coul d go up t o 35KV or mor e, causi ng some X- Ray l eakage f r om t he CRT. I n t he earl y 70s when news of t hi s r adi at i on scar e was f i r st announced, t here was a publ i c out cr y t o i mmedi at el y f i x t he pr obl em. The f eds hast i l y i mposed a r equi r ement on manuf act ur er s of TV set s t o somehow r ender a TV set unwat chabl e i f t he HV exceeded r at ed l i mi t s.
The manuf act ur er s f i r st r esponse was t o f ol l ow t he l et t er of t he l aw and t he f i r st HEW ci r cui t si mpl y bl anked t he vi deo when t he HV exceeded a set poi nt t o make t he set unwat chabl e. I t was qui ckl y not i ced t hat t he HV was not t ur ned of f wi t h t hi s ci r cui t and t he CRT st i l l coul d emi t some r adi at i on. Many TV set s wi t h t hi s f eat ur e wer e l ef t on so t he consumer coul d l i st en t o t he sound, so t he f eds t i ght ened t he r equi r ement . By t hi s t i me new TV set s wer e al l sol i d st at e and some manuf act ur er s exper i ment ed wi t h HV shut down ci r cui t s, but most of t hese ci r cui t s were poor l y desi gned and not r el i abl e. Zeni t h t hought t hey had t he answer by r egul at i ng t he HV wi t h a bank of 5 capaci t or s across t he hor i zont al out put t r ansi st or t o hol d down the HV t o 25KV. I f one capaci t or opened, t he HV woul d onl y r i se about 2KV, not a danger ous si t uat i on. Thi s wasn' t good enough f or t he f eds. The f i x t hat Zeni t h f i nal l y came out wi t h, was a 4 l egged capaci t or . Two l egs wer e t he emi t t er r et ur n f or t he hor i zont al out put t r ansi st or, & t wo l egs wer e t he HV hol ddown capaci t or ( t he equi val ent val ue of t he bank of 5 caps) . Thi s f i x was accept ed by HEW and mi l l i ons of TVs wer e pr oduced. I t wor ked so wel l , t hat ot her manuf act ur er s soon f ol l owed t he l ead ( Magnavox, GE, et c. ) . Then t he wor st happened! The 4 l egged monst er s st ar t ed f ai l i ng i n a l ar ge number s. Not openi ng compl et el y & not shor t i ng out . They somet i mes al l owed t he HV t o skyr ocket t o over 50KV. Some of t hem even cut t he necks of f of t he CRTs. Zeni t h i ssued a r ecal l on t hose model s wi t h t he pr obl em ( mor e t han one ent i r e model year ) . Af t er sever al i mpr oved ver si ons of t he capaci t or , t he pr obl em was f i xed but t hat r ecal l al most bankr upt ed t he company. Ot her compani es had f ai l ur es t oo, but usual l y not as dr amat i c as Zeni t h' s. Magnavox used t he HV hol ddown capaci t or , bot h si ngl e & 4 l eg ver si on i n sever al 70s er a TV set s and i s a good candi dat e f or f i r ewor ks as wel l . 15. 2)
Memor y chi ps i n TVs
( Fr om: Mar k Zeni er ( mzeni er @eski mo. com or
mzeni er @net com. com) ) .
Act ual l y, t hey ar e EEPROMs. A modern TV has i nt egr at ed t he ci r cui t r y so that t he mi cr opr ocessor t hat cont r ol s i t al so set s t he var i ous adj ust ment s l i ke ver t i cal hei ght and ot her char act er i st i cs. The same memor y t hat knows what channel s ar e val i d and what t he br i ght ness and other user adj ust abl e set t i ngs ar e i s used f or f act or y adj ust ment s t hat are set when t he TV i s f i r st t ur ned on. I t ' s a l ot cheaper t o use t he r emot e cont r ol si gnal s t hat ar e al r eady t her e t han add a handf ul of t r i mmer r esi st or s. For ser vi ce pur poses t her e i s of t en a magi c key sequence used wi t h your r emot e cont r ol t o access a ser vi ce page i n t he on scr een di spl ay t han can change t hese. Si nce you can easi l y set s omet hi ng t hat coul d f r y t he var i ous hi gh power def l ecti on ci r cui t s, get t i ng a l i t t l e t oo cur i ous can voi d your war r ant y, and t oast your set . 15. 3)
Tony' s not es on set t i ng conver gence on del t a gun CRTs
( Thi s sect i on f r om: ard12@eng. cam. ac. uk ( A. R. Duel l ) )
The ol der del t a- gun t ubes ( 3 guns i n a t r i angl e, not i n a l i ne) can gi ve EXCELLENT pi ct ur es, wi t h ver y good conver gence, pr ovi ded: You' ve set t hose 20- or - so pr eset s cor r ect l y - a r i ght pai n as t hey i nt er act t o some extent . The CRT i s set up i n t he f i nal posi t i on - t hi s t ype of t ube i s mor e sensi t i ve t o ext er nal f i el ds t han t he PI L t ype. Bot h my del t a- gun set s ( a B&O 3200 chassi s and a Bar co CDCT2/ 51) have ver y cl ear l y set out and l abel ed conver gence panel s, and you don' t need a ser vi ce manual t o do t hem. The i nst r uct i ons i n t he Bar co manual ar e somet hi ng l i ke: Appl y cr osshat ch, and adj ust t he cont r ol s on t he conver gence boar d i n t he number ed or der t o conver ge t he pi ct ur e. The di agr ams by each cont r ol show t he ef f ect . Her e' s a ver y qui ck gui de t o del t a gun conver gence wher e t he set t i ngs ar e done usi ng var i ous adj ust ment s on t he neck of t he CRT ( i f you don' t have a ser vi ce manual but do know what each cont r ol does, and wher e t hey al l ar e ot her wi se, f ol l ow t he i nst r uct i ons i n t he ser vi ce manual - - - sam) : Appl y a whi t e cr osshat ch or dot patt er n to t he set . Don' t t r y and conver ge on anyt hi ng el se - you' l l go i nsane. I t ' s usef ul t o be abl e t o swi t ch bet ween t hose 2 pat t er ns. Bef or e you st ar t , set t he hei ght , wi dt h, l i near i t y, pi ncushi on, et c. They wi l l i nt er act wi t h t he conver gence. Al so check PSU vol t ages, and t he EHT vol t age i f i t ' s adj ust abl e. That ' s wher e you do need a ser vi ce manual , I guess. Tur n of f t he bl ue gun usi ng t he A1 swi t ch, and use t he st at i c r adi al cont r ol s t o get a yel l ow crosshat ch i n scr een. These cont r ol s may be el ect r i cal pr eset s, or magnet s on t he r adi al conver gence yoke ( t he Y- shaped def l ecti on yoke) .
r ed and gr een t he mi ddl e of t he may be movabl e t hi nk behi nd t he
Tur n on t he bl ue gun and use t he 2 bl ue st at i c cont r ol s ( r adi al and l at er al ) t o al i gn t he bl ue and yel l ow cr osshat ches at t he cent er of t he scr een. Some manuf act ur er s r ecommend t ur ni ng of f t he gr een gun when doi ng t hi s, and al i gni ng r ed wi t h bl ue ( usi ng *onl y* t he bl ue cont r ol s, of cour se) , but I pr ef er t o al i gn bl ue wi t h yel l ow, as i t gi ves a check on t he over al l conver gence of t he t ube. Tur n of f t he bl ue gun agai n. Now t he f un st ar t s - dynami c conver gence. The f i r st adj ust ment s al i gn t he r ed and gr een cr oss hat ches near t he edges I nor mal l y do t he t op and bot t om f i r st . Ther e wi l l be 2 cont r ol s f or t hi s, ei t her a t op and a bott om, or a shi f t and a l i near i t y. The second t ype i s a PAI N t o do, as i t ' s not uncommon f or i t t o af f ect t he st at i c conver gence. Get t i ng t he r ed and gr een ver t i cal s al i gned near t he edges i s a si mi l ar pr ocess. You now have ( hopef ul l y) a yel l ow c r oss hat ch over t he ent i r e sc r een.
Now t o al i gn t he bl ue. Thi s i s a l ot wor se, al t hough t he pr i nci pl e i s t he same. Tur n on t he bl ue gun agai n, and check t he st at i c ( cent er ) conver gence To al i gn t he bl ue l i nes wi t h t he yel l ow ones, you' l l f i nd not onl y shi f t cont r ol s, but al so sl ope cont r ol s. Use t he shi f t cont r ol s to al i gn t he cent er s of t he l i nes and t he sl ope cont r ol s t o get t he endpoi nt s r i ght . These i nt er act t o some extent . You' l l need t o f i ddl e wi t h t he cont r ol s f or a bi t t o work out what t hey do, even i f you have t he manual . The conver gence over t he ent i r e sc r een shoul d now be good. . . . A word of warni ng here. . . The pur i t y i s set by ri ng magnet s on al most al l col our CRTs, but on PI L t ubes, t her e are ot her r i ng magnet s as wel l l i ke st at i c conver gence. Make sur e you know what you ar e adj ust i ng. 15. 4)
Saga and gener al set up f or l ar ge CRT TVs
( Responses f r om: Tony ( ar d12@eng. cam. ac. uk) , pani c f r om V. K. ) I ' m havi ng pr obl em( s) wi t h a br and new 40 Mi t subi shi t ube ( di r ect vi ew) TV. I ' m wr i t i ng t hi s wi t h hopes of get t i ng some basi c i nf or mat i on so t hat t he deal er doesn' t bamboozl e me. Fr om f i r st vi ewi ng ( 5 mi nut es af t er t he del i ver y man depar t ed) . I not i ced a di scol or at i on patch i n the t op ri ght hand cor ner ( pur pl e when the backgr ound i s bl ue/ gr eeni sh when backgr ound i s whi t e) . As you pr obabl y know, a col our TV pr oduces a r ed pi ct ur e, a gr een pi ct ur e and a bl ue pi ct ur e on t he scr een at t he same t i me. You eyes i nt er pr et t hat as a col our ed pi ct ur e. I f you l ook at ( a nor mal , non- pr oj ect i on) TV scr een t hr ough a magni f yi ng l ens, you shoul d be abl e t o see r ed, gr een and bl ue dot s, and no ot her col our s. Now, t her e ar e 3 basi c adj ust ment s t o get t i ng a good col our pi ct ur e : Pur i t y. Thi s means t hat t he r ed pi ct ur e i s onl y red, t he gr een pi ct ur e onl y gr een, et c. Thi s i s t he one t hat needs set t i ng up on your set - you have a pur i t y pr obl em Conver gence. Thi s means t hat t he 3 pi ct ur es l i ne up over t he ent i r e screen ( or as much of i t as possi bl e) . I f t hi s one i s wr ong, you' l l see col our ed f r i nges around obj ect s i n t he pi ct ur e. Gr ey scal e. Thi s set s t he over al l col our of t he pi ct ur e - i t means t hat whi t e i s r eal l y whi t e, et c . I t var i es t he r el at i ve i nt ens i t i es of t he red, gr een and bl ue pi ct ur es. I cal l ed t he st or e i n a pani c and t hey cal ml y t ol d me t o pr ess t he degauss but t on t o el i mi nat e t he pr obl em ( whi ch I qui ckl y l ear ned was spur i ous magnet i zat i on, caused per haps by st orage near a speaker i n t he warehouse?) . Resul t ? Bet t er but not cur ed. Yes, spur i ous magnet i zat i on ( or mor e cor r ect l y a di f f er ent magnet i c f i el d ar ound t he t ube f r om t he one pr esent when i t was set up) wi l l cause pur i t y pr obl ems. The next day I vi si t ed t he st or e, and t he manager sai d ( agai n) t hat
t hi s was an easi l y f i xabl e pr obl em, r equi r i ng a f ew waves of a degaussi ng coi l . To appease me, he sends t he sal esman home wi t h me wi t h smal l ( 1 f oot di amet er ) coi l i n t ow. Sal esman ( boy, act ual l y) waves t he coi l i n f r ont of and ar ound set and can' t seem t o per f ec t l y Ar gh. . . Her e' s what shoul d have been done I MHO. The set shoul d have been degaussed ( a f ancy wor d f or demagnet i zed) . They shoul d have connect ed a ' pat t er n gener at or ' t o t he set . Thi s i s a pi ece of equi pment t hat gener at es var i ous t est si gnal s. They shoul d have sel ect ed ' r ed r ast er ' ( whi ch wi l l appear t o you as a pur e r ed scr een) , and set up t he pur i t y adj ust ment s on t hat . You shoul d ask t o see t he pur e r ed r ast er ( and pur e gr een and pur e bl ue i f t he gener at or wi l l al l ow i t ) , and make sur e t here ar e no st r ange- col our ed pat ches. I f you l i ke, you can exami ne t he scr een t hr ough a magni f yi ng l ens t o check t hat t her e ar e no dot s of ot her col our s appear i ng - I do t hat when I ' m set t i ng up a new TV or moni t or . They shoul d t hen have di spl ayed a ' cr oss hat ch' on t he sc r een. Thi s i s a gr i d of whi t e ver t i cal and hor i zont al l i nes. Conver gence er r or s are shown by t he l i nes spl i t t i ng i nt o 2 or mor e col our s ( nor mal l y one of t he ' pr i mar y col our s' - r ed, gr een, or bl ue, and i t s compl ement ar y col our ( cyan, magent a, and yel l ow) ) . Not e, however , t hat i t ' s VERY di f f i cul t or even i mpossi bl e t o get per f ect conver gence over t he ent i r e scr een on a moder n t ube, and t hat you' l l not not i ce smal l er r or s near t he cor ner s on a TV scr een. Not e t hat some engi neer s pr ef er t o set up t he conver gence on some ot her t ype of di spl ay ( dot s, f or exampl e) , but you shoul d at l east be abl e t o see a cr oss hat ch patt er n ( al l pat t er n gener at or s pr ovi de t hat one) They shoul d have t hen di spl ayed a ' gr ey sc al e' t est di spl ay. Thi s i s a pat t er n of ver t i cal gr ey bar s of di f f er ent br i ght nesses, f r om bl ack t o whi t e. They shoul d al l have been a neut r al gr ey, wi t hout col our at i on. Not e t hat conver gence and pur i t y i nt er act t o some ext ent , and t hus i f ei t her i s adj ust ed, bot h must be checked ( and r echecked) . Gr ey scal e adj ust ment s i nt er act wi t h not hi ng el se. I woul d want t o see t he set on a pat t er n generat or ( at l east t he pat t er ns I ' ve ment i oned above) and i dent i f y t he pr obl ems. To demagnet i ze t he TV, he says t hat a l ar ge coi l i s r equi r ed, t hat encompasses t he whol e uni t ; ser vi ce r ep wi l l ' be i n t ouch' . I ' ve never hear d of t hat - t he cor r ect pr ocedur e i s t o wi pe t he coi l ar ound t he f r ont , t op, si des and bot t om NOT t he back and t hen move i t 2- 3m f r om t he set bef or e t ur ni ng i t of f . I t doesn' t mat t er whet her t he set i s on or of f f or t hi s, bt w. I ' ve not hear d of put t i ng a l ar ge coi l r ound t he ent i r e set . ( See t he sect i on: Degaussi ng ( demagnet i zi ng) CRTs) . Af t er t he sal es boy l eaves, I coul d SWEAR t hat t he pi ct ur e qual i t y i n gener al i s decreased, wi t h peopl e ( especi al l y t hei r ext r emi t i es l i ke l i ps and ear s) appear i ng pi nker t han bef ore, and al so more gener al i nt er f er ence ( f r i nges/ noi se) not i ceabl e.
The conver gence and pur i t y ar e set by r i ng magnet s on t he neck of t he t ube. I t ' s possi bl e that t he degaussi ng pr ocedur e has sl i ght l y demagnet i zed t hese, and i f so, t he whol e set wi l l need t o be set up. Si mi l arl y, i f any part of t he set was magnet i zed at t he f act or y, t hen t he adj ust ment s may have been set up t o compensat e, and t hen af t er demagnet i zati on, t hey' l l need t o be r eset . So my quest i ons ar e t hese. Can t he ori gi nal pr obl em t r ul y be FI XED wi t h pr oper si zed coi l and appl i cat i on? I don' t t hi nk the si ze of t he coi l wi l l make any di f f er ence. I woul d want t o see t hat set on a pat t er n gener at or , so I coul d be SURE as t o what t he pr obl ems are. I f t he deal er s don' t have a pat t er n gener at or , t hen t hey' r e not f i t t o be f i xi ng TVs I MHO. Coul d I be i magi ni ng t hat t he wavi ng of t he smal l coi l degr aded t he pi ctur e qual i t y? I t ' s pos si bl e, but f ai r l y unl i kel y. See above Shoul d I demand r epl acement t o a new set ? Can I l egal l y ask f or t hi s, or i s i t l i ke a new car . . . you own i t , now you deal wi t h t he ser vi ce guys f or ever . I don' t know US l aw, but i n t he UK, i f a pr oduct i s def ect i ve, you can demand a r ef und of t he money pai d ( not a r epl acement or a r epai r , a r ef und) . I MHO, a TV wi t h i ncor r ect col our s i s def ect i ve. . . 15. 5)
About I nst ant On TVs
Most TVs bui l t si nce, say, 1980 have onl y t he mi cr ocont r ol l er power ed f r om a smal l t r ansf ormer when t he set i s of f . Thi s per mi t s t he r emot e cont r ol or f r ont panel pushbut t on t o swi t ch t he set on. Thi s ci r cui t r y shoul d be no mor e pr one t o cat ast r ophi c f ai l ur e t han what i s i n a VCR or di gi t a l cl ock. Hi st or i cal l y, t her e wer e ' i nst ant on' TVs whi ch kept a subst ant i al por t i on of t hei r ci r cui t r y l i ve al l t he t i me - especi al l y those usi ng vacuum t ubes i n at l east par t of t he ci r cui t r y ( ot her t han t he CRT) . I n t hese, t her e was a l ot more t o f ai l . Those t ubes woul d cont i nue t o change t hei r char act er i st i cs f or many mi nut es when war mi ng up. Ci r cui t s wer e al so much mor e t ouchy - r emember al l t hat const ant t weaki ng! Thus, i t made sense f r om t he user s' s per spect i ve t o el i mi nat e t he war mup per i od and keep t hose t ubes t oast y al l t he t i me. I n moder n sol i d st at e TVs, t he onl y component t o r eal l y need a war mup per i od i s t he CRT. Al l t hi s means i s t hat you have t o wai t 20 seconds f or t he pi ct ur e t o appear. 15. 6)
Can I add an S- Vi deo i nput t o my TV or VCR?
Possi bl y, but why bother ? VCR' s ci r cui t r y anyhow. Al l S- Vi deo means i s: A speci al connect or Separ at e l umi nance ( Y)
You wi l l most l i kel y be l i mi t ed by t he TV or
Chr omi nance ( C) r at her t han composi t e vi deo. I n a VCR, you wi l l need t o bypass t he i nput ci r cui t r y and get t o t he pl ace wher e Y and C ar e separ at e. Thi s may or may not be possi bl e dependi ng on i t s desi gn. I n a TV, t hey may never be separ at e and you wi l l need t o subst i t ut e your own ci r cui t r y f or t he chr oma demodul at or. I t i s pr obabl y not wor t h i t as you wi l l l i kel y not gai n much i n pi ct ur e qual i t y but i f you r eal l y ar e det er mi ned, a schemat i c wi l l be essent i al i n ei t her case. I f al l you want t o do i s al l ow f or an S- vi deo i nput , t her e ar e si ngl e chi ps whi ch wi l l combi ne t he Y and C i nt o a nor mal composi t e vi deo s i gnal . Al so, see t he sect i on: How do I add A/ V i nput s t o a TV whi ch does not have t hem bui l t i n? si nce t her e may be saf et y i mpl i cat i ons i n t he case of addi ng S- Vi deo t o a TV wi t hout any A/ V j acks . 15. 7)
How do I add A/ V i nput s t o a TV whi ch does not have t hem bui l t i n?
The pl ace t o do t hi s i s af t er t he vi deo and audi o I F wher e baseband si gnal s ar e normal l y separ at e. Dependi ng on t he model of TV, t hi s may be tr i vi al t o i mpossi bl e - or a ser i ous saf et y hazar d. Tr i vi al : many l ow- end model s use t he same chass i s as t he hi gh end A/ V r ecei ver s. Ei t her t her e wi l l a cabl e connect i on t o t he mi ssi ng A/ V panel , or a whi ch woul d have t he A/ V i nt er f ace and j acks. I f your model , t hen i t shoul d be st r ai ght f orwar d and c i r c ui t s at t hat poi nt .
( r ead t hi s: ci r cui t boar d) be some par t s mi ssi ng, mi ssi ng auxi l i ary boar d t hi s i s t he case wi t h saf e t o t ap i nt o t he
I f , on t he ot her hand, ever ythi ng i s cr ammed ont o a si ngl e ci r cui t boar d wi t h no evi dence of A/ V si gnal s, i t may be ver y di f f i cul t as sui t abl e t ap- i n poi nt s may si mpl y not be avai l abl e. Hazar dous: many TVs have ci r cui t r y whi ch i s not i sol at ed f r om t he AC l i ne. I f t hi s i s t he case wi t h your set , t hen i t may be mor e t r oubl e t han i t i s wort h t o pr ovi de t he essent i al i sol at i on barr i er bet ween t he TV and your ext er nal A/ V equi pment . Unl ess you i nt end t o al ways use t he di r ect A/ V i nput s and f orgo t he t uner , you wi l l need some way of sel ect i ng bet ween t hem - a swi t ch or r el ay. Thi s coul d be manual - you push a but t on or f l i p a swi t ch - or aut omat i c. Ther e ar e al l ki nds of ways t o doi ng t he det ect i on - mechani cal , checki ng f or a l ow i mpedance connect i on, l ooki ng f or a si gnal , usi ng a swi t ch, et c. You wi l l need a sc hemat i c - don' t at t empt t hi s wi t hout one ( f or saf et y, i f no ot her r eason) . 15. 8)
Tur ni ng a TV ( or moni t or) i nt o an osci l l oscope?
Thi s quest i on comes up so of t en and i t does sound l i ke a neat pr oj ect t o
gi ve a def unct TV a second l i f e. Don' t expect t o end up wi t h a Tek 465 on t he cheap when you ar e done. However , i t coul d be a f un l ear ni ng exper i ence. You wi l l be sever el y l i mi t ed i n t he per f or mance of such a scope. TVs and moni t or s ar e desi gned t o oper at e at a very nar r ow r ange of hori zont al scan r at es and t he hi gh vol t age i s usual l y der i ved f r om t he hor i zont al def l ect i on. So, you woul d need t o r et ai n t he or i gi nal def l ect i on syst em f or t hi s pur pose at l eas t . You wi l l need t o di sc onnect t he def ect i on yoke f r om t he hor i zont al and ver t i cal def l ecti on ci r cui t s of t he TV or moni t or wi t hout ki l l i ng t he HV. ( al so, doi ng al l t hi s wi t hout ki l l i ng your sel f as wel l ) . Dependi ng on t he desi gn, t hi s may be as si mpl e as unpl uggi ng t he yoke connect or . Mor e t han l i kel y, you wi l l need t o subst i t ut e a l oad f or t he hor i zont al def l ec t i on c oi l . A c oi l f r om anot her s ac r i f i c i al s i mi l ar TV or moni t or woul d pr obabl y suf f i ce. WARNI NG: at t hi s poi nt you have a r eal l y br i ght spot i n t he mi ddl e of t he screen whi ch wi l l t ur n t o a r eal l y bl ack spot i f t he br i ght ness i s not t ur ned way down r eal l y r eal l y qui ckl y. For t he hor i zont al , you need a r amped cur r ent sour ce. You are dr i vi ng a non- i deal i nduct or ( t he def l ect i on coi l ) so i t has bot h i nduct ance and r esi st ance. Thus t he wavef or m i s a t r apezoi d - a vol t age r amp ( f or t he r esi st i ve par t ) super i mposed on a vol t age step ( f or t he i nduct i ve par t ) . Thi s shoul d not be t oo di f f i cul t . Don' t expect t o be abl e t o achi eve r eal l y f ast sweep. Even r unni ng at nor mal TV r at es i s non- t r i vi al . Si mi l ar l y, f or t he ver t i cal you need t o dr i ve wi t h a vol t age ( your si gnal ) cont r ol l ed cur r ent sour ce. However , i f you j ust scr ewi ng ar ound, t hen the l i near i t y et c. f or t he ver t i cal may not be t hat i mpor t ant . I n t hi s case, one way i s t o put a cur r ent sensi ng r esi st or i n ser i es wi t h t he def l ect i on coi l and use t hi s i n a power op amp t ype of f eedback ar r angement . ( You coul d do t hi s f or ( 2) as wel l . Ther e i s a good chance t hat t he or i gi nal br i ght ness cont r ol wi l l wor k as an i nt ensi t y adj ust ment . However , wi t h some TVs and moni t or s, t hi s depends on r ecei vi ng a val i d vi deo si gnal . You may need t o i mpr ovi se. I f you do want t o cont r ol t he i nt ensi t y f r om a si gnal sour ce, you shoul d be abl e t o tap i nt o the dr i ve si gnal s goi ng t o t he l i t t l e boar d on t he neck of t he CRT. Don' t expect hi gh bandwi dt h, uni f or m r esponse, or any of t he ot her t hi ngs you t ake f or gr ant ed wi t h a decent scope. That t akes work. However , as a f un pr oj ect , t hi s cer t ai nl y qual i f i es. I nt er changi ng t he f unct i ons of t he hor i zont al and ver t i cal def l ect i on yoke ( and r ot at i ng i t 90 degr ees) may pr ovi de a bet t er mat ch of hor i zont al and ver t i cal bandwi dt h t o your i nt ended appl i cat i ons or exper i ment s. SAFETY: Once you di sconnect t he def l ect i on yoke f r om t he TV or moni t or' s ci r cui t s, move t he or i gi nal ci r cui t s out of t he way and put a bar r i er bet ween bet ween you and t he r est of t he TV or moni t or . Al l you wi l l need ar e connect i ons t o t he def l ect i on yoke on t he CRT ( unl ess you want t o do i nt ensi t y modul at i on) . Wi t h a col or TV or moni t or, such experi ment s coul d be pr et t y i nt er est i ng but t her e may be col or f r i ngi ng ef f ect s si nce you ar e not compensat i ng f or cer t ai n aspect s of dynami c conver gence at al l .
15. 9)
Di spl ayi ng a vi deo si gnal as a pi ct ur e on an osci l l oscope
I am not sur e why anyone woul d r eal l y want t o do t hi s ot her t han as an exper i ment - i t woul d be i nt er est i ng one. I f a composi t e vi deo si gnal i s t he i nput , you wi l l need a sync separ ator . You wi l l have t o const r uct a ver t i cal def l ect i on vol t age r amp gener at or whi ch can be l ocked t o your ver t i cal sync si gnal . The hor i zont al t i mebase of t he sc ope wi l l be f i ne f or t he hor i zont al def l ect i on and shoul d easi l y l ock t o your hor i zont al sync pul se or ( i f t he scope has a TV t r i gger mode) di r ect l y to t he vi deo si gnal . A vi deo ampl i f i er wi l l be needed i f your Z axi s does not have an i nt ernal ampl i f i er ( you need . 7 V p- p t o be f ul l br i ght ness r ange. ) Unl ess you pr ovi de aut omat i c gai n cont r ol , t hi s wi l l need t o i ncl ude of f set ( br i ght ness) and gai n ( cont r ast ) adj ust ment s. Even i f t her e i s an i nt er nal ampl i f i er , i t may not have t he r equi r ed bandwi dt h f or t he vi deo si gnal . However , t he over al l br i ght ness may be di sappoi nt i ng - a scope i s not desi gned f or over al l hi gh br i ght ness. The beam f ocus wi l l not be as good as t hat on a l i t t l e TV ei t her . 15. 10)
Use of s ur ge suppr essors and l i ne f i l t er s
Shoul d you al ways use a sur ge suppr essor out l et st r i p or l i ne ci r cui t ? Sur e, i t shoul dn' t hur t . J ust don' t depend on t hese t o pr ovi de pr ot ect i on under al l ci r cumst ances. Some ar e bet t er t han ot her s and t he mar ket i ng bl ur b i s at best of l i t t l e hel p i n maki ng an i nf or med sel ect i on. Pr oduct l i t er at ur e - unl ess i t i s backed up by t est i ng f r om a r eput abl e l ab - i s usual l y pr et t y usel ess and of t en conf usi ng. Li ne f i l t er s can al so be usef ul i f power i n you ar ea i s noi sy or pr one t o spi kes or di ps. However , keep i n mi nd t hat most wel l desi gned el ect r oni c equi pment al r eady i ncl udes bot h sur ge suppr essor s l i ke MOVs as wel l as L- C l i ne f i l t er s. Mor e i s not necessar i l y bet t er but may move t he poi nt of f ai l ur e t o a r eadi l y accessi bl e out l et st r i p r at her t han t he i nnar ds of your equi pment i f damage occur s. Ver y ef f ect i ve pr ot ect i on i s possi bl e t hr ough t he use of a UPS ( Uni nt er r upt i bl e Power Suppl y) whi ch al ways r uns t he equi pment of f i t s bat t er y f r om t he i nt er nal i nver t or ( not al l do) . Thi s pr ovi des ver y ef f ecti ve i sol at i on power l i ne pr obl ems as t he bat t er y act s as a huge capaci t or . I f somet hi ng i s damaged, i t wi l l l i kel y be t he UPS and not your expensi ve equi pment . Anot her opt i on i s t o use a const ant vol t age t r ansf ormer ( SOLA) whi ch pr ovi des vol t age r egul at i on, l i ne condi t i oni ng, and i sol at i on f r om power spi kes and sur ges. I t i s s t i l l bes t t o unpl ug ever yt hi ng i f t he ai r r ai d s i r ens go of f or you see an el ephant wear i ng t hi ck gl asses r unni ng t hr ough t he nei ghbor hood ( or an i mpendi ng l i ght eni ng st or m) . 15. 11)
GFCI t r i ppi ng wi t h moni t or ( or ot her hi gh t ech equi pment )
Gr ound Faul t Ci r cui t I nt er r upt er s ( GFCI s) ar e ver y i mpor t ant f or
mi ni mi zi ng shock hazar ds i n ki t chens, bat hr ooms, out door s and ot her pot ent i al l y wet ar eas. They ar e now gener al l y r equi r ed by t he NEC Code i n t hese l ocat i ons. However , what t he GFCI det ect s t o pr ot ect peopl e - an i mbal ance i n t he cur r ent s i n t he Hot and Neut r al wi r es caused possi bl y by someone t ouchi ng a l i ve conduct or - may exi st saf el y by desi gn i n hi gh t ech el ect r oni c equi pment . The r esul t - f al se t r i ppi ng - i s most l y a pr obl em wi t h 3 wi r e gr ounded devi ces wi t h bui l t i n l i ne f i l t er s havi ng capaci t or s bet ween Hot and Gr ound but may al so occur wi t h 2 wi r e ungr ounded TVs due t o t he power - on sur ge i nt o t he hi ghl y capaci t i ve or i nduct i ve l oads of t hei r power suppl i es. 15. 12)
Mul t i syst em TVs
The quest i on of t en ar i se: can my NTSC TV modi f i ed t o di spl ay PAL si gnal s ( or vi ce- ver sa) . Unl i ke a VCR wher e t her e ar e subst ant i al di f f er ences bet ween r ecordi ng of NTSC and PAL, t he pr obl em of di spl ayi ng t he pi ct ur e i s much si mpl er . The f ol l owi ng ass umes 525 l i ne NTSC and 625 l i ne PAL: The hor i zont al scan r at es ar e near l y i dent i cal ( 15, 734 Hz f or NTSC and 15, 625 Hz f or PAL) , so t hi s i s not l i kel y t o be a pr obl em. I f t hese di f f er ed si gni f i cant l y, t hen t her e woul d be desi gn i ssues si mi l ar t o t hose f or mul t i sync comput er moni t or s and t hi s woul d dr i ve up cost . The ver t i cal sc an ar e sl i ght l y mor e of a pr obl em wi t h 525 l i ne/ 60 Hz NTSC and 625 l i ne/ 50 Hz PAL. But i t i s a l ot easi er t o desi gn ver t i cal def l ect i on t o accommodat e a modest var i at i on i n r at es. TVs coul d be easi l y desi gned or modi f i ed to accept ei t her . The col or encodi ng t echni ques di f f er but i nexpensi ve I Cs exi st t hat can deal wi t h ei t her st andar d. I n f act , many ar e pr ogr ammabl e t o do ei t her wi t h a j umper and sl i ght modi f i cat i ons t o the ext er nal component s. Di spl ayi ng a monochr ome - B/ W - pi ct ur e on t he ot her ki nd of set i s usual l y possi bl e i f t he set has a ver t i cal hol d cont r ol or enough ver t i cal r ange. Modi f yi ng t he chr oma ci r cui t r y i s more compl i cat ed but i t shoul d be possi bl e t o subst i t ut e a second I C and patch i t i nt o t he exi st i ng vi deo chai n. As f ar as commer ci al mul t i syst em TVs ar e concer ned, t he r eal r eason we do not s ee many of t hese ( at l east i n t he U. S. ) i s l ack of demand. They ar e avai l abl e i f you l ook hard enough and ar e wi l l i ng t o pay a pr emi um. They ar e r eadi l y avai l abl e on t he i nt er nat i onal mar ket . 15. 13)
Coul d a TV be modi f i ed f or 3D ( st er eo) di spl ay?
The whol e i dea of st er eo 3- D vi si on t o put t he l ef t and r i ght vi ews t o t he appr opr i at e eyebal l . Ther e ar e t wo common ways of doi ng t hi s: Use di f f er ent col or s f or t he t wo vi ews wi t h col or f i l t er s i n f r om of each eye t o separ at e t he vi ews. Thi s i s what wer e of t en used f or t he r eal l y bad ( cont ent wi se) sci - f i movi es of t he ' 50s. Di spl ay al t er nat e vi ews on t he same moni t or scr een but use LCD shut t er gl asses t o al l ow each eye t o onl y see t he appr opr i at e vi ew. Thi s r equi r es i ncr easi ng t he r ef r esh r at e t o avoi d unaccept abl e f l i cker .
The f i r st appr oach can be used wi t h any TV and a pai r of monochr ome vi deo camer as. Of cour se, t r ue col or cannot be used si nce pur e col or ed i mages ar e needed t o separ at e t he st er eo vi ews. Al t er nat i ng vi ews on a st andar d TV, dut y cycl e whi ch i your vi ewer s wi l l 15. 14)
wi t h synchr oni zed LCD t he r esul t i ng r ef r esh s l i kel y to be usef ul l i kel y devel op spl i t t i
gl asses i s a possi bi l i t y but r at e woul d be 30 Hz wi t h a 50% onl y as a shor t exper i ment - el se ng headaches.
Di spl ayi ng TV on a comput er moni t or
My gener al r ecommendat i on i s t hat i f you have t he space, buy an i nexpensi ve TV - t he qual i t y i n t he end may i n f act be bet t er . And, i t wi l l be usabl e wi t hout t yi ng up your expensi ve moni t or and ( maybe) PC. Whi l e var i ous conver t or s ar e adver t i zed t o use a comput er moni t or wi t h vi deo f r om a VCR or ot her sour ce, keep i n mi nd t hat i f i t sounds t oo good t o be t r ue, i t pr obabl y i s l i ke t he cl ai m of a $200 box f or t hi s: OK, l et me get t hi s st r ai ght - t hi s car d/ box wi l l enabl e a 31. 4 KHz hor i zont al scan r at e moni t or ( VGA) be used as a TV - yes or no? I t t hus i ncl udes a vi deo A/ D, f ul l screen f r ame buf f er , D/ A, and al l t he ot her t uner st uf f f or under $200? I don' t t hi nk so. A scan doubl er - whi ch i s a subset of t he above wi l l not r es ul t i n a hi gh qual i t y pi c t ur e s i nc e i t wi l l di s pl ay pai r s of l i nes i nt er l eaved. Or does t he i mpr essi ve adver t i sement l eave out t he key r equi r ement t hat t he moni t or s ync at t he NTSC hor i zont al scan r at e of 15. 734 KHz ( most newer moni t or do not ) ? Or i s i t a boar d t hat pl ugs i nt o a PC and i ndeed does use t he r esour ces of t he PC i ncl udi ng t he VGA car d and bus? I n any case, get a wr i t t en money back sat i sf act i on guar ant ee. 15. 15)
Di spl ayi ng comput er vi deo on a TV
Ass umi ng t hi s means NTSC: You need t o conver t RGB t o NTSC - t her e ar e si ngl e chi ps f or t hi s. Tr y Sony, Phi l i ps, Motor ol a, and ot her s. These wi l l combi ne t he R, G, B, H sync, and V sync i nt o a si ngl e composi t e vi deo si gnal usi ng a mi ni mum of addi t i onal component s. You need t o mat ch t he sc an r at e t o NTSC - 15. 734 KHz hor i zont al . Even basi c VGA i s t wi ce t hi s - 31. 4 KHz. I f your vi deo car d can be pr ogr ammed t o put out i nt er l aced NTSC r at e vi deo t hen t hi s i s easy. I f not , i t i s mor e di f f i cul t . I f you want t o use anythi ng hi gher r es t han VGA, i t i s a ver y non- t r i vi al pr obl em r equi r i ng t he const r uct i on of a scan conver t or whi ch i ncl udes a vi deo A/ D, f ul l f r ame st or e, i nt er pol at or / r eadout t i mi ng, vi deo D/ A. Unl ess you are an exper i enced di gi t al / anal og desi gner , you r eal l y do not want t o tackl e any of t hi s. For t he speci al case of VGA- >NTSC, you may be abl e t o get away wi t h j ust st or i ng a si ngl e scan l i ne si nce t he hor i zont al f r equency i s ( al most ) exact l y t wi ce t he NTSC hor i zont al of 15. 734 KHz. A doubl e buf f er wher e one buf f er i s st or i ng whi l e t he ot her i s r eadi ng out at appr oxi mat el y hal f t he VGA pi xel r at e shoul d wor k. Wi t h appr opr i at e t i mi ng, even l i nes become t he even f i el d f or NTSC and odd l i nes become t he odd f i el d ( I may have t hi s backwar ds) . I t i s st i l l not a t r i vi al under t aki ng. Al so, keep i n mi nd
t hat t he qual i t y you wi l l get on NTSC wi l l be poor er t han t he VGA due t o f undament al NTSC bandwi dt h l i mi t at i ons. Al so, f l i cker f or l i ne gr aphi cs wi l l be si gni f i cant due t o t he i nt er l aci ng at 30 Hz. Even t hi s i s a non- t r i vi al under t aki ng. The r equi r ement s f or PAL ar e ver y si mi l ar . For 625 l i nes syst ems, t he 800x600 i s t he f ormat t hat most cl osel y mat ches t he TV r esol ut i on. You can al so buy l i t t l e boxes t o do t hi s. Qual i t y i s gener al not gr eat as you ar e ser i ousl y l i mi t ed by NTSC/ PAL and t he VCR. Except f or pr esent at i ons on exi st i ng TV r at e equi pment , i t i s pr obabl y not wor t h t he ef f or t . Thi s i s total l y usel ess f or any ser i ous comput er appl i cat i ons. For pr of essi onal pr esent ati ons, moder n vi deo pr oj ect or s ar e avai l abl e t hat use hi gh r esol ut i on LCD panel s and r eal - t i me scan conver si on. However , t hey ar e qui t e expensi ve ( up t o $10, 000! ! ! ) . 15. 16)
What i s Kel l f act or wi t h r espect t o i nt er l aced di spl ays?
( The f ol l owi ng i s f r om Bob Myer s ( myer s@f c. hp. com) ) . The Kel l f act or - whi ch has t o do wi t h t he f act t hat we' r e of t en under sampl i ng an i mage f r om t he st andpoi nt of t he Gospel Accor di ng t o St . Nyqui st - I S a f actor i n t he r educti on of ver t i cal r esol ut i on, but i nt er l aci ng pl ays a par t as wel l . Thi s comes f r om at l east t wo f act or s: The r ecei ver usual l y cannot pr eci sel y i nt er l eave t he t wo f i el ds. Mor e i mpor t ant l y, t her e ar e steps t aken to r educe t he i nt er l i ne f l i cker whi ch r educe t he ef f ect i ve ver t i cal r esol ut i on. Thi s i ncl udes runni ng t he l i ne wi dt h of t he di spl ay somewhat l ar ger t han woul d ot her wi se be t he case, and i n i nt er l aced camer as, di schar gi ng t he ent i r e scr een ( i ncl udi ng t he l i nes f r om t he ot her f i el d) af t er ever y f i el d scanned. I nt er l ace i s par t i cul ar l y t r oubl esome on movi ng i mages, wher e you wi l l of t en per cei ve moment ar i l y mi ssi ng det ai l s. Ther e was a LOT of di scussi on r egar di ng t he gory det ai l s of i nt er l aci ng i n the r ecent HDTV debat es wi t hi n SMPTE and ot her gr oups. 15. 17)
Homemade V- chi p ( or at l east vi ewi ng l i mi t er
Her e i s an i nt er est i ng quest i ons: I woul d l i ke a cont r ol box of some sor t t hat cont r ol s t he cabl e si gnal t hat comes i nt o t he TV. I want t o be abl e t o cont r ol t he t ot al t i me a par t i cul ar chi l d has i n hi s account t o wat ch, pl us t he act ual channel s t hat he i s al l owed t o wat ch ( no Pl ayboy or MTV) , PLUS t he t i me of day t hat he can wat ch ( not dur i ng home wor k t i me) . Pr ogr ammabl e by channel , cumul at i ve t i me, hour of t he day, and day of t he week. I al so need a mast er pass wor d f or par ent al pr ogr ammi ng of t he ki ds account s, pl us be abl e t o wat ch what I want t o at any t i me. The ki ds coul d use ei t her an i ndi vi dual account number or an i ndi vi dual car d of some ki nd wi t h a PI N l i ke our ATM car ds. Thi s box shoul d be secur e so t hat a 14 year ol d boy can' t bypass i t ver y easi l y. At l east wi t hout doi ng come maj or damage so t hat I ' d know i t when he di d i t . I know t hat t hi s i s a l ot t o ask, but I ' m ver y f ami l i ar wi t h comput er pr ogr ammi ng and
chi pset t echnol ogy, I do know t hat such a t hi ng can be done. I j ust don' t have t he el ect r oni cs knowl edge t o do i t . The f ol l owi ng pr obabl y won' t hel p you bui l d such a gi zmo but her e ar e some t hought s: Fi r st , I woul d not att empt t o bui l d any of t he RF/ cabl e swi t chi ng st uf f - t her e ar e t oo many var i at i ons. I woul d suggest t r yi ng t o cont r ol t he cont r ol of what you have. Wi t h a cabl e box, t hi s woul d be r el at i vel y easy - j ust put t he box and an I R t r ansmi t t er i n the same seal ed encl osur e. I f you have onl y a cabl e r eady TV, you coul d subst i t ut e or i nt er cept t he r emot e det ect or si gnal i nsi de t he set and di sabl e t he f r ont panel cont r ol s. Then you need: An i nput devi ces - keypad f or exampl e. A di spl ay - a 1 l i ne LCD. A mi cr opr ocessor . Thi s doesn' t need t o be much - j ust t o st ore t he ' account i nf or mat i on' i ncl udi ng bal ance, al l owabl e channel and t i me sl ot map, passwords. I t woul d need a r eal t i me cl ock. An I R r emot e code t r ansmi t t er . Thi s coul d pr obabl y be di r ect l y pr ogr ammed by t he mi cr o t o cont r ol your cabl e box. Each account woul d have a means of addi ng t o t he bal ance, password aut hent i cat i on, et c. You woul d have a super user account f or your own wat chi ng as wel l as changi ng any of t he i ndi vi dual account set t i ngs. Too bad I don' t st i l l t each my i nt r o t o comput er desi gn cour ses - t hi s woul d make a ni ce t erm pr oj ect . I f you have a j unker PC, t hi s woul d be a si mpl e bi t of pr ogr ammi ng ( but qui t e wast ef ul of power even f or an 8088 based PC) . 15. 18)
I nt er est i ng TV Swi t ch Mode Power Suppl y
The f ol l owi ng was f ound i n a Sony TV: Q1 swi t chi ng/ r eg t r a ns i s t or ( +) --- - - - +- - - - - - - - - - - - - | | - - - - - - - - - +- - - - - - - - - - - | ---- | | --| _| _ AC - - - | | - - | = C1 | | di ode / _\ D2 i n -- -| |- -- -- -| -- -| +- - - - - +- - - - - - + | | ---(-) | | Reg. Dr i ve | C | D1 | +- - - - - +- - - - - - + C choke +- - - - gnd | | C _|_ | | | +135 cap __ _ C2 | | | I---> |+ +- - - - - - - - - - +- - - - - - - - - - +- - - - - - - - - - - +- - - - + 135 Al t hough at f i r st t hi s appear s t o shor t out t he l i ne suppl y, when dr awn l i ke t hi s i t t ur ns out t o be a val i d swi t chi ng r egul at or : Q1 i s dr i ven by a pul se wi dt h modul at ed si gnal a t he hori zont al r at e.
Q1 t ur ns on put t i ng 150 V acr oss choke. Cur r ent r amps up i n choke - mor e or l ess l i near unt i l sat ur at i on whi ch shoul d not occur . Thi s ti me i ncreases wi t h i ncr easi ng l oad. Q1 t ur ns of f . Si nce cur r ent i n an i nduct or cannot change i nst ant l y, cur r ent cont i nues t o f l ow, now t hr ough D2, C2, and +135 l oad. LCR ( R of l oad, di ode) t i me const ant - char ges capaci t or and power s l oad. I t woul d appear t o f ai l and r un away under t he f ol l owi ng ci r cumst ances: I nduct ance i s t oo l ow and choke cannot st or e enough ener gy even at hi gh dut y cycl e t o suppl y l oad. Too hi gh a dut y cycl e and core sat ur at es at whi ch poi nt t r ansi st or bl ows up. I nduct ance i s t oo hi gh r el at i ve t o swi t chi ng f r equency so t hat choke does not have t i me t o di schar ge (i t s cur r ent ) bef or e next cur r ent pul se DC cur r ent wi l l j ust keep i ncreasi ng unt i l cor e sat ur at es. Thi s coul d onl y r eal l y happen i f t he swi t chi ng f r equency wer e t oo hi gh f or some r eason unl ess someone changed cor e mat er i al or somet hi ng l i ke t . Load i s t oo gr eat due t o f aul t el sewher e. When at t empt i ng t o di agnose pr obl ems wi t h t hese t ypes of ci r cui t s wher e t he nat ur al out come of a f aul t i s f or one or mor e expensi ve par t s t o f ai l cat ast r ophi cal l y, i t i s wi se t o ei t her use a Var i ac to br i ng up t he i nput vol t age sl owl y and car ef ul l y obser ve t he behavi or hopef ul l y bef ore t oo l ate or put a l oad i n ser i es wi t h t he l i ne such as a 100W l i ght bul b t o l i mi t t he cur r ent ( t hough t hi s wi l l change t he behavi or i n var i ous ways) . 15. 19)
I R det ector ci r cui t
Thi s I R Det ect or may be used f or t est i ng of I R r emot e cont r ol s, CD pl ayer l aser di odes, and ot her l ow l evel near I R emi t t er s. Component val ues ar e not cr i t i cal . Pur chase phot odi ode sensi t i ve t o near I R - 750- 900 um or s al vage f r om opt ocoupl er or phot osensor . Dead comput er mi ce, not t he f ur r y ki nd, usual l y cont ai n I R sensi t i ve phot odi odes. For conveni ence, use a 9V bat t er y f or power . Even a weak one wi l l wor k f i ne. Const r uct so t hat LED does not i l l umi nat e t he phot odi ode! The det ect ed si gnal may be moni t or ed at t he col l ect or of t he t r ansi st or ( Q1) wi t h an osci l l oscope. Vc c ( +9 V) >- - - - - - - +- - - - - - - - - + | | | \ / / R3 \ R1 \ 500 / 3. 3K / \ __|__ | _\ _/ _ LED1 Vi si bl e LED __ | __ | I R - - - - > _/ _\ _ PD1 +- - - - - - - - > Scope moni t or poi nt Sensor | | Photodi ode | B |/ C +- - - - - - - | Q1 2N3904
| |\ E \ | / R2 +- - - - - - - - > GND \ 27K | / | | | GND >- - - - - - - - +- - - - - - - - - + _ | _ Chapt er 16) 16. 1)
I nt er nati onal Col or Tel evi si on St andar ds
Some quest i ons and answer s about TV st andar ds
( Responses f r om: St eve McKi nt y: ( smcki nt y@f r ance. sun. com) ) Q: What ar e t he most common TV st andar ds i n t he wor l d? NTSC Nat i onal Tel evi si on St andar ds Commi t t ee PAL Phase Al t er nat e Li ne SECAM SEquent i al Coul eur Avec Memoi r e ( Sequent i al col our wi t h memor y) Ther e ar e ot her di f f er ences t hough. St r i ct l y t hey ar e j ust di f f er ent col our syst ems, but most count r i es whi ch use PAL have 625 l i nes i n a pi ct ur e and send 25 f ul l pi ct ur es/ second, most NTSC count r i es have 525 l i nes and send 30 f ul l pi ct ur es/ second ( most l y f or hi st or i cal r at her t han t echni cal r easons) . That compl i cat es t hi ngs. Q: Who devi sed t hem, and when? and why? Ar e t hey as ol d as t el evi si on? The f i r st ser i ous TV exper i ment i ng was done i n sever al count r i es ar ound t he per i od 1900- 1930, most l y bl ack & whi t e. The BBC st ar t ed a r egul ar ser vi ce i n 1936, ot her count r i es f ol l owed soon af t er , but si nce t he t echnol ogy was devel opi ng ver y r api dl y t her e wer e al ways i mpr ovement s bei ng made. The BBC st ar t ed wi t h 405 l i nes, t he US st ar t ed a ser vi ce a coupl e of year s l at er wi t h 525, by t he t i me ot her Eur opean count r i es st ar t ed t he t echnol ogy al l owed 625 l i nes. France even tr i ed 819 l i nes. Al l t hose syst em wer e bl ack & whi t e, but peopl e want ed t o have col our . Dur i ng t he 1940' s much of Eur ope was at war , and t echnol ogi cal devel opment f or ent er t ai nment sl owed down, but i n t he US t hey wer e abl e t o cont i nue and devi sed a col our syst em whi ch was compat i bl e wi t h t he exi st i ng bl ack & whi t e one. By compat i bl e I mean t hat a bl ack & whi t e TV got a bl ack & whi t e pi ct ur e, a col o( u) r one got a col our pi ct ur e. No need t o make peopl e t hr ow away t hei r B&W TVs. Thi s s yst em was endor sed by t he Amer i can Nat i onal Tel evi si on St andar ds Commi t t ee, and was named af t er i t => NTSC. Af t er t he war ot her count r i es st art ed t o l ook at col our . NTSC was a ver y cl ever syst em, but i t had some f l aws. Engi neer s i n var i ous count r i es t r i ed t o i mpr ove on i t , and Tel ef unken i n Ger many came up wi t h a si mpl e modi f i cat i on whi ch i mpr oved col our st abi l i t y. I t was named PAL because t hey r ever sed t he Phase of t he col our si gnal on
Al t er nat e Li nes. At t he same t i me Henr i de Fr ance, i n Fr ance, f i xed t he same f l aw i n a di f f er ent way. Hi s desi gn ( SECAM) needed a memor y i nsi de t he set whi ch made i t mor e expensi ve. PAL gave as good a r esul t , so most count r i es opt ed f or t hat . Fr ance st ayed wi t h SECAM, possi bl y because i n t he De Gaul l e er a of t he 50' s memor i es of Ger man occupat i on wer e st i l l f r esh, and dr oppi ng a Fr ench syst em i n f avour of a German one woul d have been unpopul ar . Rumour has i t t hat t he Fr ench gover nment subsi di zed Thompson t o make memor y af f or dabl e. Si nce Br i t ai n went PAL, Fr ance went SECAM, and t he US went NTSC, any col oni es or dependenci es of t hose count r i es t ended t o get t he same syst em. I ndi a/ Paki st an got PAL, Al ger i a got SECAM, and si nce t he US hel ped r ebui l d J apan af t er WW2 i t got NTSC, et c. Q: What' s t he di f f er ence? To squeeze a col our si gnal i nt o t he same space as a bl ack & whi t e one, and st ay compat i bl e, t he NTSC desi gner s s epar at ed t he col our and br i ght ness i nf or mat i on. The human eye i s l ess sensi t i ve t o col our , so t hey wer e abl e t o r educe t he bandwi dt h of t hat si gnal ( make i t t ake up l ess space i n each channel ) , ' hi di ng' i t at t he hi gh- f r equency end of t he vi deo. That meant t hey di dn' t need t o make t he channel s bi gger , and i ncompat i bl e. To do t hat , t hey used t he f act t hat you can r epr esent most col our s wi t h a combi nat i on of Red, Gr een and Bl ue. I f you f i l m a scene wi t h t hr ee camer as, one f or each col our , t hen add al l t he out put s t oget her you get a bl ack & whi t e i mage. Thi s si gnal i s cal l ed l umi nance, usual l y r epr esent ed by ' Y' . Mat hemat i cal l y Y = R + G + B. ( Act ual l y, not al l t he cont r i but i ons ar e equal ) . They t hen t r ansmi t t ed t he Y si gnal j ust as f or a bl ack & whi t e TV, and al so t r ansmi t t ed t he R and B i n t he ext r a col our si gnal . B&W TV' s onl y saw Y, and col our TV' s got Y, R and B. Si nce Y = R + B + G, G can be obt ai ned as Y - ( R+B) , so t hey di dn' t need t o t r ansmi t al l t hr ee. To get bot h R and B i nt o one si gnal , t hey use a combi nat i on of Phase and Ampl i t ude modul at i on ( t hi nk of i t as AM and FM at t he same t i me) . I t s cal l ed quadr at ur e modul ati on, and wor ks ver y wel l , but i s suscept i bl e t o phase changes as i t passes al ong cabl es, et c. I f t he si gnal get s +10 degr ees phase change t he col our wi l l vi si bl y change, whi ch i s why NTSC TV' s have a t i nt cont r ol . PAL over comes t hat by sendi ng R and +B on one l i ne, t hen R and - B on t he next . That way a +10 phase shi f t on one l i ne becomes - 10 on t he next , and smal l di f f er ences wi l l cancel out . PAL TV' s don' t need t i nt cont r ol s. SECAM doesn' t send bot h R & B t oget her , i t sends R on one l i ne, B on t he next . No f ancy modul at i on, so no phase pr obl ems, but you need a ' memor y' i n t he set t o save up t he si gnal f r om t he pr evi ous l i ne, si nce bot h R & B are r equi r ed t oget her f or pr ocessi ng. Q: Why do you need di f f er ent TVs? Most l y because of t he di f f er ent number s of l i nes. I t s qui t e easy t o make one col our decoder whi ch can cope wi t h al l t he syst ems, but
maki ng a TV whi ch can do 625 and 525 l i nes, 25 and 30 pi ct ur es/ second, get s expensi ve. Consumer s shop on pr i ce, no- one wi l l buy a SECAM TV i n t he USA even i f i t onl y cost s $20 mor e, si nce t her e ar en' t any SECAM channel s. Q: Why do you need di f f er ent VCRs? Q: Why can' t one VCR r ecor d t he same out put ? Some can, but l i ke TVs i t cost s mor e t o make t hem adj ust . The mot or speed vari es wi t h t he number of pi ct ur es t r ansmi t t ed per second, f or exampl e. ( Thi s i s cover ed i n more det ai l i n t he document : Not es on t he Di agnosi s and Repai r of Vi deo Casset t e Recor der ( VCR) Not es on t he VCR Fai l ur e Di agnosi s and Repai r . ) Q: Why di d di f f er ent syst ems evol ve? Q: I s one cheaper ? Q: I s one bet t er ? When or i gi nal l y devel oped, expense was consi der ed based on cont empor ar y t echnol ogy. As not ed, pol i t i cs may have been equal l y i mpor t ant . As t o whi ch has bet t er qual i t y, i t s al l r at her subj ect i ve. The 625- l i ne syst em adopt ed i n Eur ope has bet t er ver t i cal r esol ut i on t han t he 525- l i ne US syst em, but some peopl e f i nd t he 50Hz f i el d r at e st i l l pr oduces some f l i cker . NTSC/ PAL/ SECAM are al l equal l y capabl e of excel l ent col our r epr oduct i on, but under poor si gnal condi t i ons NTSC can degr ade mor e qui ckl y. Q: Ar e t her e ot her syst ems besi des t he ones I ' ve ment i oned? Why? Some ot her s, l i ke MAC wher e t he col our and l umi nance ar e compl et el y separ ated. That get s r i d of i nt er f er ence ( ever see t he st r ange col our s whi ch appear on ver y f i ne check pat t erns?) but i s more expensi ve and r eal l y onl y possi bl e due t o moder n el ect r oni cs. Q: Ar e t her e goi ng t o be mor e or l ess syst ems i n t he f ut ur e? That i s THE quest i on! Ther e ar e cer t ai nl y goi ng t o be di f f er ent syst ems, more l i nes, bet t er sound, et c. Q: I s t her e any way t o conver t a PAL t ape t o NTSC or vi ce ver sa? Yes. I f t he PAL t ape has 625 l i ne pi ct ur es and t he NTSC one has 525 l i ne t hen you nor mal l y need a comput er whi ch can r ead i n one f or mat and r e- adj ust t hi ngs. Not cheap, but becomi ng cheaper , sever al compani es of f er t hat sor t of ser vi ce. Some PAL VCRs can do a hal f - conver si on, enough to f ool most PAL TVs i nt o t hi nki ng i t s got a PAL si gnal . Q: Do they t each t hi s st uf f i n el ect r i cal engi neer i ng cour ses? Somet i mes. 16. 2)
Some of i t , depends a l ot on t he cour se and school .
Pol i t i cal l y Cor r ect TV St andar ds
( The f ol l owi ng i s f r om: Rober t Rol f ) . SECAM
Used by Fr ance and t he f or mer No t i nt cont r ol . No Ful l soci al i sm. The shoul d see, and how
Sovi et uni on. col or cont r ol . st at e knows exact l y what col or you st r ong t hat col or shoul d be.
PAL Used by Ger many & UK, Aust r al i a et c. No t i nt c ont r ol . A c ol or c ont r ol . Par t i al soci al i sm. The st at e knows exact l y what col or you shoul d see, but you get a choi ce as t o how st r ong i t can be. NTSC Used i n USA and Canada, J apan et c. A t i nt c ont r ol , A c ol or c ont r ol . Uncont r ol l ed soci al i sm. The st at e l et s you chose what col or you see and how st r ong i t can be. They t hen t ax you r egar dl ess. J ust anot her way of l ooki ng at i t . . . . 16. 3)
Var i at i ons on a ' st andard' - t he PAL syst em
I n t he U. S. , when PAL i s ment i oned, i t i s usual l y assumed t o be 625 l i ne/ 50 Hz as used i n t he UK and man ot her pl aces. However , t her e ar e sever al var i at i ons on t he PAL sys t em. ( The f ol l owi ng f r om: Ed El l er s
Col or t el evi si on st andards wor l dwi de
( The f ol l owi ng i s f r om EDMUNDO, Desi gn Engi neer Ten- Lab) We at Ten- Lab have put t oget her t he f ol l owi ng chart l i st i ng count r i es
and t hei r
cor r espondi ng col or TV st andar ds.
We ar e t r yi ng t o be as accur at e as possi bl e, but we need your f eedback t o r ef i ne and cor r ect t he i nf ormat i on. We ar e doi ng t he best we can i n spi t e of i nher ent pr obl ems such as: Some of t he l i t er at ur e and char t s ar e cont r adi ct or y; even some books and manual s cont r adi ct each ot her mor e t han t hey agr ee. Many count r i es have changed t hei r names dur i ng t he l ast f ew year s. Some count r i es have one br oadcast TV syst em, but al so r ecei ve pr ogr ams i n a di f f er ent syst em f r om beyond t hei r border s. Thi s cr eat es some conf usi on about t he f or mat ( s) used l ocal l y. I NTERNATI ONAL TV STANDARDS CHART by TEN- LAB ( UPDATED J an 19, 1996) COUNTRY VHF STANDARD UHF STANDARD AFGANI STAN PAL/ SECAM B ALBANI A PAL B PAL G ALGERI A PAL B PAL G ANGOLA PAL I ARGENTI NA PAL N PAL N AUSTRALI A PAL B PAL G AUSTRI A PAL B PAL G AZORES PAL B BAHAMAS NTSC M BAHRAI N PAL B PAL G BANGLADESH PAL B BARBADOS NTSC M BELGI UM PAL B PAL H BERMUDA NTSC M BOLI VI A NTSC M BOTSWANA PAL I BOURKI NA FASO SECAM K1 BRAZI L PAL M PAL M BRUNEI PAL B BULGARI A SECAM D SECAM K BURMA NTSC M BURUNDI SECAM K1 CAMBODI A NTSC M CAMEROON PAL B PAL G CANADA NTSC M NTSC M CANARY I SLANDS PAL B CHAD SECAM K1 CHI LE NTSC M NTSC M CHI NA PAL D COLOMBI A NTSC M NTSC M COSTA RI CA NTSC M NTSC M CUBA NTSC M NTSC M CYPRUS PAL G PAL G CZECHOSLOVAKI A: now CZECH REPUBLI C PAL PAL SLOVAK REPUBLI C PAL PAL DAHOMEY SECAM K1 DENMARK PAL B PAL G DJ I BHOUTI SECAM B SECAM G DOMI NI CAN REP NTSC M NTSC M
ECUADOR EGYPT EL SALVADOR EQUATORI AL GUI NEA ETHI OPI A FI J I FI NLAND FRANCE FRENCH POLYNESI A GABON GAMBI A GERMANY GHANA GI BRALTAR GREECE GREENLAND GUADELOUPE GUAM GUATEMALA GUANA ( FRENCH) GUI NEA HONDURAS HONG KONG HUNGARY I CELAND I NDI A I NDONESI A I RAN I RAQ I RELAND I SRAEL I TALY I VORY COAST J AMAI CA J APAN J ORDAN KENYA KOREA NORTH KOREA SOUTH KUWAI T LEBANON LI BERI A LI BYA LUXEMBOURG MADAGASCAR MADEI RA MALAGASY MALAWI MALAYSI A MALI MALTA MARTI NI QUE MAURI TANI A MAURI TI US MEXI CO MONACO MONGOLI A MOROCCO
NTSC M NTSC M SECAM B SECAM G NTSC M NTSC M PAL B PAL B PAL G PAL B PAL B PAL G SECAM L SECAM L K1 SECAM K1 PAL I PAL B PAL G PAL B PAL G PAL B PAL H SECAM/ PAL B SECAM/ PAL G NTSC M/ PAL B SECAM K1 NTSC M NTSC M NTSC M SECAM K1 PAL K NTSC M NTSC M PAL I SECAM D/ PAL SECAM K/ PAL PAL B PAL G PAL B PAL B PAL G SECAM B SECAM G SECAM B PAL I PAL I PAL B PAL G PAL B PAL G SECAM K1 NTSC M NTSC M NTSC M PAL B PAL G PAL B PAL G SECAM D NTSC M NTSC M PAL B SECAM B SECAM G PAL B PAL H SECAM B SECAM G PAL B PAL G/ SECAM L SECAM K1 PAL B SECAM K1 PAL B PAL G PAL B SECAM K1 PAL B PAL H SECAM K1 SECAM B SECAM B NTSC M NTSC M SECAM L SECAM D SECAM B
MOZAMBI QUE PAL B NAMI BI A PAL I NEPAL PAL B NETHERLANDS PAL B PAL G NETH. ANTI L LES NTSC M NEW CALEDONI A SECAM K1 NEW GUI NEA PAL B PAL G NEW ZEALAND PAL B PAL G NI CARAGUA NTSC M NI GER SECAM K1 NI GERI A PAL B NORWAY PAL B OMAN PAL B PAL G PAKI STAN PAL B PANAMA NTSC M PARAGUAY PAL N PERU NTSC M PHI LI PPI NES NTSC M POLAND SECAM D/ PAL PORTUGAL PAL B PAL G PUERTO RI CO NTSC M QATAR PAL B REUNI ON SECAM K1 RUMANI A PAL D RUSSI A SECAM D RWANDA SECAM K1 SABAH/ SARAWAK PAL B ST. KI TTS NTSC M SAMOA NTSC M SAUDI ARABI A SECAM B/ PAL SENEGAL SECAM K1 SEYCHELLES PAL B PAL G SI ERRA LEONE PAL B SI NGAPORE PAL B PAL G SOMALI A PAL B SOUTH AFRI CA PAL I SPAI N PAL B PAL G SRI LANKA PAL B SUDAN PAL B SURI NAM NTSC M SWAZI LAND PAL B PAL G SWEDEN PAL B SWI TZERLAND PAL B SYRI A SECAM B TAHI TI SECAM K1 TAI WAN NTSC M TANZANI A PAL B THAI LAND PAL B TOGO SECAM K TRI NI DAD Y TOBAGO NTSC M TUNI SI A SECAM B TURKEY PAL B UGANDA PAL B UNI TED ARAB EMI RATES PAL B UNI TED KI NGDOM UPPER VOLTA SECAM K1 URUGUAY PAL N USA NTSC M
NTSC M
NTSC M PAL G PAL G NTSC M NTSC M NTSC M SECAM K/ PAL NTSC M PAL K SECAM K NTSC M B
SECAM G
PAL G PAL G PAL I PAL G NTSC M PAL G PAL G NTSC M PAL B NTSC M PAL PAL PAL PAL
G G G I
PAL N NTSC M
VENEZUELA VI ETNAM YEMEN YUGOSLAVI A ZAI RE ZAMBI A ZI MBABWE 16. 5)
NTSC M PAL B PAL B PAL B SECAM K1 PAL B PAL B
NTSC M PAL G PAL G PAL G PAL G
Cabl e channel al l ocat i on
( The f ol l owi ng i s f r om: ( kruskal @wat son. i bm. com ( Vi ncent Kr uskal ) ) . The f ol l owi def i ned i n St andar ds, gat her ed.
ng t abl e gi ves t he def i ni t i ons of t he numer i c cabl e channel s t he EI A ( El ectr oni c I ndust r i es Associ at i on) I nt er i m I S- 6 ( CP) , May 1983 and associ at ed i nf or mat i on t hat has been Def i ni t i ons appear at t he end.
HRC Pi ctur e Channel Car r i er -------- ------1 72 MHz 2 54 3 60 4 66 5 78 6 84
Cabl e Band ----------Low ( VAR) Low Low Low Low Low
7 8 9 10 11 12 13
174 180 186 192 198 204 210
Hi Hi Hi Hi Hi Hi Hi
14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
120 126 132 138 144 150 156 162 168 216 222 228 234 240 246 252 258 264 270 276 282 288
Mi d Mi d Mi d Mi d Mi d Mi d Mi d Mi d Mi d Super Super Super Super Super Super Super Super Super Super Super Super Super
Ot her Names ------------------------- A- 8, C54, J 54, G64, 4+, 5A
A- 7, C55, J 55, G65 A- 6, C56, J 56, G66
gh gh gh gh gh gh gh ( ATC) ( ATC) ( VAR) ( VAR) ( VAR) ( VAR) ( VAR) ( VAR) ( VAR) ( VAR)
A B C D E F G H I J K L M N O P Q R S T U V
36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93
294 300 306 312 318 324 330 336 342 348 354 360 366 372 378 384 390 396 402 408 414 420 426 432 438 444 450 456 462 468 474 480 486 492 498 504 510 516 522 528 534 540 546 552 558 564 570 576 582 588 594 600 606 612 618 624 630 636
Super Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Hyper Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a
( HAM) ( HAM) ( HAM) ( HAM) ( HAM) ( HAM)
( RA)
W AA, W+1 BB, W+2 CC, W+3 DD, W+4 EE, W+5 FF, W+6 GG, W+7 HH, W+8 I I , W+9 J J , W+10 KK, W+11 LL, W+12 MM, W+13 NN, W+14 OO, W+15 PP, W+16 QQ, W+17 RR, W+18, C62 SS, W+19, C63 TT, W+20, C64 UU, W+21, C65 VV, W+22, C66 WW, W+23, C67 AAA, W+24, C68 BBB, W+25, C69 CCC, W+26, C70 DDD, W+27, C71 EEE, W+28 U14, FFF, W+29 U15, GGG, W+30 U16, HHH, W+31 U17, I I I , W+32 U18, J J J , W+33 U19, KKK, W+34 U20, LLL , W+35 U21, MMM, W+36 U22, NNN, W+37 U23, OOO, W+38 U24, PPP, W+39 U25, QQQ, W+40 U26, RRR, W+41 U27, SSS, W+42 U28, TTT, W+43 U29, UUU, W+44 U30, VVV, W+45 U31, WWW, W+46 U32, AAAA, W+47 U33, BBBB, W+48 U34, CCCC, W+49 U35, DDDD, W+50 U36, EEEE, W+51 U37, FFFF, W+52 U38, GGGG, W+53 U39, HHHH, W+54 U40, I I I I , W+55 U41, J J J J , W+56 U42, KKKK, W+57
94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 16. 6)
642 90 96 102 108 114 648 654 660 666 672 678 684 690 696 702 708 714 720 726 732 738 744 750 756 762 768 774 780 786 792 798
Ul t r a Low ( FM) Low ( FM) Low ( FM) Low Low Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a Ul t r a
U43, A- 5, A- 4, A- 3, A- 2, A- 1, U44, U45, U46, U47, U48, U49, U50, U51, U52, U53, U54, U55, U56, U57, U58, U59, U60, U61, U62, U63, U64, U65, U66, U67, U68, U69,
LLL L, W+58 C57, J 57 C58, J 58 C59, J 59 C60, J 60, G60 C61, J 61, G61 MMMM, W+59 NNNN, W+60 OOOO, W+61 PPPP, W+62 QQQQ, W+63 RRRR, W+64 SSSS, W+65 TTTT, W+66 UUUU, W+67 VVVV, W+68 WWWW, W+69 AAAAA, W+70 BBBBB, W+71 CCCCC, W+72 DDDDD, W+73 EEEEE, W+74 FFFFF, W+75 GGGGG, W+76 HHHHH, W+77 I I I I I , W+78 J J J J J , W+79 KKKKK, W+80 LLL LL, W+81 MMMMM, W+82 NNNNN, W+83 OOOOO, W+84
Not es on cabl e and br oadcast f r equenci es
( The f ol l owi ng i s f r om: kr uskal @wat son. i bm. com ( Vi ncent Kr uskal ) ) . RF band To get t he band, subt r act 1. 25 f r om pi ct ur e car r i er ( l ow end) and add 4. 75 ( hi gh end) . Col or subcar r i er Add 3. 58. . . t o pi c t ur e c ar r i er . Sound car r i er : Add 4. 5 t o pi cture car r i er . HRC Harmoni cal l y Rel at ed Carr i er . Makes bot h second- and t hi r d- order beat s i nvi si bl e by maki ng t hem f al l di r ectl y on t he pi ctur e car r i er of ot her channel s. That i s, mul t i pl yi ng t he pi ct ur e car r i er by t wo or t hr ee wi l l yi el d exactl y anot her pi ctur e car r i er . I RC I ncr ement al l y Rel at ed Car r i er , add 1. 25 t o HRC f r equency. A Gener al I nst r ument s ( J er r ol d) cat al og sai d t hat I RC makes t hi r d- or der ( mor e i mpor t ant t han second- or der ) beat s i nvi si bl e by maki ng them f al l di r ectl y on t he pi cture car r i er of other channel s. But i t i s not t r ue
t hat mul t i pl yi ng an I RC pi ct ur e car car r i er by t wo or t hr ee yi el ds an anot her I RC pi ct ur e car car r i er . Thi s con cont r adi ct i on has not be been r esol sol ved ved. The r eason son t hi r d- or der har moni cs ar ar e more i mpor t ant ant i s t hat osci l l at or s and and ampl i f i er s t end end t o gen gener at e odd odd- or der der har moni oni cs f ar mor e t han han even even-- or der one ones. Br oad oadcast f r equ equency ency Add 1. 25 t o HR HRC f r eque equency ncy excep exceptt f or chann channel el s 5 and and 6. For For t hem, sub subt r act 0. 75. But t hese are j ust nomi nal f r equenci es. The FCC FCC act ual l y has t hr ee channel channel desi gnat gnat i ons f or each number as i n 5, 5- and and 5+. The The mi nus nus channe channell s ar e 10 10 kHz kHz bel bel ow t he nomi nal nal val ue and and t he pl us chan chann nel s ar ar e 10 kHz kHz ab above. ove. For For exam exampl e: ( next ext sect i on) on) 16. 16. 7)
Why i s t he NTSC TSC col or subcar subcar r i er such a wei r d f r equ equency? ency?
( The f ol l owi ng i f f r om Bob Myer yer s ( myer yer s@f c. hp. com com) ) . Act ual l y, i f we want ed t o de def i ne the r at es t o t he Nt h de degr ee, t he i mpor t ant st ar t i ng poi nt i s t he f i el d r ate. The NTSC col col or f r ame r at e was def def i ned as ( 60 * 100 1000/ 1001) Hz, whi ch i s a bi t mor e t han 59. 94 Hz. From From t hi s rate, rate, al l t he ot her s i n t he syst syst em ar e def i ned. The l i ne r at e i s 26 262. 5 t i mes t hi s, and t he col col or sub subcar car r i er i s de def i ned as 45 455/ 2 t i mes t he l i ne r at e. Thi Thi s i s of of t en gi ven ven as si mpl y 3. 579545 MHz, but t he t he col col or sub subcar car r i er was actua actuall l y der i ved f r om t he l i ne/ f i el d r at es rather rather t han han t he ot her her way ar ound ound.. The whol e t hi ng was done done so as t o avoi d ( or at l east mi ni mi ze) i nt er act i on bet bet ween t he l umi nance, nance, chr omi nance, nance, and and audi audi o subcom subcomponen ponentt s i n t he st and andar d col or si gnal . Thi Thi s cou coul d have ave been ach achi eved ved by movi ovi ng ei t her t he audi o sub subcar car r i er or adj adj ust i ng t he l i ne/ f r ame r at es as de descr i bed abo above; ve; unf or t unat el y, t he l at t er r out e was cho chosen sen, l eavi ng us wi t h t hi s ve ver y st r ange- l ooki ng set set of r at es. The pr eci se col or bur st f r equency equency wi nds nds up bei ng 3. 57954 579545. 5. 4545. 4545. . . under under t hi s de def i ni t i on, but gi vi ng i t t o t he near est Hz i s wi t hi n t he t ol er ances ces of t he syst syst em. 16. 8)
What i s t he maxi axi mal al l owed devi at i on of t he hor i zont zont al f r equency? ency?
( The f ol l owi ng i s f r om: Pet Pet er Bennet t VE7CEI ( bennet t @t r i umf . ca) ca) ) I n Can Canad ada a an and t he US US ( 525 l i ne, 60 HZ, NTSC TSC) , t he hori hori zont zont al f r equ equency i s 15, 734. 264 Hz. The col col our sub subcar car r i er i s 45 455/ 2 t i mes t he hori zon zont al f r eque equency ncy whi ch shou shoull d come t o 3. 3. 5795 579545 45 MHz. I bel bel i eve eve t he t ol er ance ance on on t he sub subcar car r i er f r equency i s +/ - 10 Hz. 16. 16. 9)
I nf or mal compar par i son of TV st and andar ds
Q: I heard t hat TV i n cer cer t ai n part of Eur ope ope has more qu qual i t y i n Eur ope ope t hen her e i n Nort h Amer i ca. ca. I ' d l i ke t o know know t he di f f er ence ences s be bet ween t he t wo syst ems. I s t hat wh why we cant cant use vi deo deo t apes apes f r om t her e? ( Responses esponses f r om: Mar k Zen Zenii er ( mzeni er @net net com. com or mzeni er @eski mo. com) ) The f i r st di f f er ence i s t hat a l ot of t he wor l d r uns uns on 50 Hz power as op opposed posed t o Nor t h Amer i ca' s 60 Hz pow power . I n t he ol den den days, ays, bef bef or e act i ve power s uppl y r egul at ors got che cheap, ap, i t was de deci ded t hat t he ver ver t i cal scan r at e mat ch t he power sup suppl y f r equ equency, so t hat r i ppl e
i n t he power supp suppl y woul oul dn' t pr odu oduce obn obnoxi oxi ous ous vi sual sual ef f ect s. So t he PA PAL/ SECAM si gnal s have have 50 vert vert i cal scans scans per per secon second. I don' t know know t he exact xact r eason soni ng, but t he hor i zon zont al scan scan r at e i s cl ose t o t he same. 1575 15750 0 ( now 1573 15734) 4) f or 60 Hz, and and 1562 15625 5 f or 50 Hz syst ems. My guess i s t he t r adeo adeoff f bet ween een cost ( 50 year year s or so ag ago) and audi bi l i t y f or a l ar ge por t i on of t he popul at i on. So 50 Hz syst ems have have mor e l i nes nes - 625 vs. vs. 525 l i nes f or 60 Hz sys t ems. The second sec ond di f f er ence i s t hat Eur Eur opean opean TV channel channel s ar e wi der . 7 or 8 MHz compar par ed t o t he Nor t h Amer i can 6 MHz. Vi deo deo band bandw wi dt h i s l i mi t ed t o 4. 2 MHz i n a 6 MHz channel channel , but can be as much as 6 MHz i n some of t he 50 Hz syst ems. ( NOTE: TE: Syst ems i s pl ur al . Ther Ther e ar e many any di f f er ent ent Eur Eur opea opean n syst ems wi t h i ncompat i bl e col or and and sound sound t r ansm ansmi ssi on met hods. ods. ) As f or t he qual i t y, i f you move a l i t t l e f ar t her away, so t hat a pi xel on each each syst em subt subt ends ends t he same ang angll e, NTSC TSC doesn' doesn' t have have a poor poor er pi ctur ctur e, j ust a sm smal l er one. Chapt apt er 17 17) 17. 17. 1)
Repai r I nf or mat i on and and Par Par t s Sou Sourr ces ces
Advan vanced TV t r oub oubl eshoo eshoott i ng
I f t he sol sol ut i ons ons t o you yourr pr obl obl ems have have not been een cove coverr ed i n t hi s docu docum ment , you you st i l l have ave some opt opt i ons ons ot her t han surr ender i ng you your TV t o t he l ocal ocal ser vi ce cen cent er or t he dumpst er . ( Al so see see t he r el at ed docum ocument ent : Sour Sour ces of Repai epai r I nf or mat i on and and Gener ener al Comment ent s. ) Manuf actur ctur er ' s servi ce l i t er at ur e Ser vi ce manu anual s ar e ava avaii l abl abl e f or a gr gr eat eat deal eal of consum consumer el ect r oni oni cs. Once you you have ave exh exhaust aust ed t he obvi obvi ous po possi bi l i t i es, t he cost cost may be wel l wor t h i t . Dependi ng on t he t ype ype of equi equi pment ent , t hese can r ang ange i n pr i ce f r om $10- 50 or mor e. Some ar e mor e usef ul t han ot hers . However ver , not al l i ncl ude t he sche schemat i cs so i f you you ar e hopi ng t o r epai r an el ect r oni c pr pr obl obl em t r y t o che check bef or e buyi ng. I nsi de cove coverr of t he e eq qui pment : TVs TVs of t en have s ome ki nd of ci r cui t di agr am past ed i nsi de t he back cove coverr . I n t he ol d days, t hi s was a com compl et e sche schemat i c. Now, i f one exi st s at at al l , i t j ust s hows pa par t number s an and l ocat ocat i on f or key compone onent s - st i l l ver ver y usef ul . Some TVs TVs - as l at e as 10 year s ago, maybe even now - i ncl uded uded a compl et e schem schemat i c wi t h t he pr odu oduct i nf or mat i on and and owner ' s manu anual . I have ave a 1984 Mi t sub subi shi shi whi ch has thi s. I t i s, however ver , t he exce xcept i on r at her t han t he r ul e any anym mor e. SAM SAMs Phot Phot of act s These have been been publ publ i shed f or over 45 year s ( I don' don' t know know f or how l ong ong but I have have SAM SAMs f or a 19 1949 por t abl abl e ( 3 i nch) nch) Pi l ot TV abou aboutt as por por t abl abl e as as an of of f i ce t ypew ypewr i t er ( i f you you r emember what one one of of t hose was l i ke) ke) and and ar ar e ge gener al l y t he best best most consi consi st ent sour sour ce of ser ser vi ce i nf o f or TVs ( near l y eve everr y mode odel t hat has eve ever been sol d) ,
r adi adi os, some VCRs an and ot her consu consum mer el ect ect r oni oni cs. t hey ar ar e i ndi spe spensab sabl e.
For For TV ser vi ci ng,
Ther e ar e s ome Comput er f act s but t he num number of t hese i s ver y l i mi t ed. The VCRf act s ar e al s o somewhat l i mi t ed and t he newer ones t end t o have st r i ctl y mecha chani cal cal i nf or mat i on. SAMs ar ar e of t en ava avai l abl e ( f or phot oco ocopy cost cost s) f r om you you l ocal cal l arge publ i c l i br ar y whi ch may sub subscr i be t o t he com compl et e ser ser i es. I f not , a l ar ge el ect r oni c di di st r i but or can can or der t he sel sel ect ed f ol der f or you. One ad advan vant age age of of t he SA SAMs i nf o i s t hat i t i s compi l ed i n a ve ver y consi consi st ent f ormat so t hat once once you you are f ami l i ar wi t h on one mode odel TV, TV, i t i s ea easy t o t r ansf er t hat kno knowl edge t o any ot her . The They pr ovi de wavef avef or ms at key l ocat i ons and and DC vol t age measur ement ent s al most eve ever ywher e. Addi t i onal onal i nf o such such as I C pi n t o gr oun ound and and coi l r esi st ances ces ar ar e of t en pr ovi ovi ded as wel l . The manuf act ur er ' s ser ser vi ce manu anual s ar e gener ener al l y not not near ear l y as as compl et e. ( BTW, I have have no conne connect ct i on wi t h SAM SAMs. ) 17. 2)
Ser vi ce manual s f or r eal l y ol d TVs
Tr y your l ar ge publ publ i c l i br ar y f or SAM SAMs phot phot of act s . I f ound ound a 3 TV of f r om ar oun ound 1948 at a yar yar d save. save. Ther Ther e was no pr obl obl em f i ndi ng a compl et e manual i ncl udi ng sch schemat i cs, par t s l i st , t r oubl esho shoot i ng pr pr oced cedur es, et c. Someday, ay, I may eve even get ar oun ound t o f i xi ng i t . Al l t he pape aper cap capaci t or s ar ar e l eaky ( f or s t ar t er s ) . BTW, t he case f or t hi s 3 TV TV i s about about 18 x 10 10 x 15 and and i t i ncl udes a hand andy opt opt i on: a 6 i nch sem semi sph spher i cal cal wat er f i l l ed magni f i er . The CRT i s an osci l l oscop scope t ube. Not you your basi basi c por t abl e! 17. 3)
Par t s i nf or mat i on
I have ave f oun ound one one of of t he most usef ul si ngl e sour sour ces ces f or general i nf or mat i on on semi condu conduct ct or s t o be be t he ECG ECG Sem Semi condu conduct ct or s Mast er Repl acem cement Gui de, about $6 f r om your l ocal cal Phi l i ps di di st r i but or . STK STK, NTE, TE, and and ot her her s have have si mi l ar manua anuall s. The The ECG ECG manua anuall wi l l enab enabll e you you t o l ook ook up up U. U. S. , f or ei gn, and and manu anuf act act ur er ' house' ouse' number s and and i dent i f y devi ce t ype ype, pi nout out , and and ot her i nf or mat i on. on. Not e t hat I am not not necessar ecessar i l y r ecom ecommendi endi ng usi ng ECG ( or ot her gener ener i c) r epl epl acem acement ent s i f t he or or i gi nal r epl acem cement s are ( 1) r eadi l y av avai l abl e an and ( 2) r eason sonabl y pr i ced ced. However ver , t he cr oss ref er ence can save save coun count l ess hour our s searchi searchi ng t hr ough ough dat aboo abooks ks or or cont cont act i ng t he manuf anuf act ur er s. Even ven i f you you have ave a wal l of dat abooks, ks, t hi s sou sour ce i s i nval uabl e. A cou coupl e of cave cavea at s: ( 1) ECG cr osses osses have have been kn known t o be be i ncor cor r ect ect - t he spe speci f i cat cat i ons ons of t he ECG r epl ace acement part wer e i nf er i or t o t he or i gi nal . ( 2) Don' t assum assume that that t he spe speci f i cat cat i ons pr pr ovi ded f or t he ECG part ar e i dent i cal cal t o t he or i gi nal - t hey hey may be bet t er i n some ways. ays. Thu Thus, usi ng t he ECG ECG t o de det er mi ne t he spe speci f i cat cat i ons of t he par t s i n you your j unk bi bi n can can be r i s k y. Ot her cr oss r ef er ence gui des are ava avaii l abl e f r om t he part s sour sour ce l i st ed bel ow. 17. 4)
I nf ormat i on sour sour ces ces on t he I nt er net
Many manuf act ur er s ar e now pr ovi di ng ext ensi ve i nf or mat i on vi a t he Wor l d Wi de Web. The answer t o you quest i on may be a mouse cl i ck away. Per f or m a net sear ch or j ust t r y t o guess t he manuf act ur er ' s home page addr ess. The most obvi ous i s of t en cor r ect . I t wi l l usual l y be of t he f orm ht t p: / / www. xxx. com wher e xxx i s t he manuf act ur er s' name, abbr evi at i on, or acr onym. For exampl e, Hewl et t Packar d i s hp, Sun Mi cr osyst ems i s sun, Mot orol a i s, you guessed i t , mot or ol a. El ect r oni c part s manuf act ur er s of t en have det ai l ed dat asheet s f or t hei r pr oduct of f er i ngs . 17. 5)
Suggest ed r ef er ences
A good sour ce f or t echnol ogy i nf ormat i on i s Basi c Theor y of Col our Tel evi si on f r om Phi l i ps. Ask t hi s book f r om your l ocal t echni cal bookst or e. ( The f ol l owi ng f r om: ( xt ar el ex@power gr i d. el ect r i ci t i . com) ) For a t echni cal r ef erence on t he var i ous f l avour s of NTSC, PAL, and SECAM used ar ound t he worl d, I suggest : Recommendat i ons and r epor t s of t he CCI R, vol ume XI , par t 1 Avai l abl e f r om Omni com, 115 Par k St . S. E. Vi enna, VA 22180 ( 703) 281- 1135 Ther e don' t seem t o be near l y as many TV r epai r books f or moder n sol i d st at e TVs as I r ecal l f or ol d t ube set s. Her e ar e i s one suggest i on whi ch you may f i nd ( or i t s pr edecessor) at your l ocal publ i c l i br ar y ( 621. 384 i f you l i br ar y i s number ed that way) or a t echni cal book st ore. MCM El ect r oni cs has t hi s as wel l . Tr oubl eshoot i ng and Repai r i ng Sol i d St at e TVs Homer L. Davi dson 2nd Edi t i on, 1992 TAB Books, I nc. Bl ue Ri dge Summi t , PA 17214 17. 6)
I nt erchangeabi l i t y of component s
Q: I f I cannot obt ai n an exact r epl acement or i f I have a moni t or, TV, or other equi pment car cass gat her i ng dust , can I subst i t ut e a par t t hat i s not a pr eci se mat ch? Somet i mes, t hi s i s si mpl y desi r ed t o conf i r m a di agnosi s and avoi d t he r i sk of order i ng an expensi ve r epl acement and/ or havi ng t o wai t unt i l i t ar r i ves. For saf et y r el at ed i t ems, t he answer i s gener al l y NO - an exact r epl acement par t i s needed t o mai nt ai n t he speci f i cat i ons wi t hi n accept abl e l i mi t s wi t h r espect t o l i ne i sol at i on, X- r ay pr ot ect i on and t o mi ni mi ze f i r e hazar ds. Typi cal par t s of t hi s t ype i ncl ude f l amepr oof r esi st or s, some t ypes of capaci t or s, and speci f i c par t s deal i ng wi t h CRT hi gh vol t age regul at i on. However , dur i ng t est i ng, i t i s usual l y accept abl e t o subst i t ut e el ectr i cal l y equi val ent par t s on a t empor ar y basi s. For exampl e, an or di nar y 1 ohm r esi st or can be subst i t ut ed f or an open 1 ohm f l amepr oof r esi st or t o det er mi ne i f t her e ar e ot her pr obl ems i n t he hor i zont al def l ect i on ci r cui t s bef or e pl aci ng an or der - as l ong as you don' t get l azy and negl ect t o i nst al l t he pr oper t ype bef or e but t oni ng up t he moni t or or TV. For ot her component s, whet her a not qui t e i dent i cal subst i t ut e wi l l wor k
r el i abl y or at al l depends on many f act ors. Some def l ect i on ci r cui t s ar e so car ef ul l y mat ched t o a speci f i c hor i zont al out put t r ansi st or t hat no s ubs t i t ut e wi l l be r el i abl e. Her e ar e some gui del i nes: Fuses - exact same cur r ent r ati ng and at l east equal vol t age rat i ng. I have of t en sol der ed a nor mal 3AG si ze f use ont o a smal l er bl own 20 mm l ong f use as a subst i t ut e. Resi st or s, capaci t or s, i nduct or s, di odes, swi t ches, pot ent i omet er s, LEDs, and ot her common par t s - except f or t hose speci f i cal l y marked as saf et y- cri t i cal - subst i t ut i on as l ong as t he r epl acement par t f i t s and speci f i cat i ons shoul d be f i ne. I t i s best t o use t he same t ype - met al f i l m r esi st or , f or exampl e. But f or t est i ng, even t hi s i s not a har d and f ast r ul e and a car bon r esi st or shoul d wor k j ust f i ne. Rect i f i er s - many are of t hese ar e hi gh ef f i ci ency and/ or f ast r ecover y t ypes. Repl acement s shoul d have at equal or bet t er PRV, I max, and Tr s peci f i c at i ons . Tr ansi st or s and t hyr i st or s ( except HOTs and SMPS chopper s) - subst i t ut es wi l l gener al l y work as l ong as t hei r speci f i cat i ons meet or exceed t hose of t he or i gi nal . For t est i ng, i t i s usual l y ok t o use t ypes that do not qui t e meet al l of t hese as l ong as t he br eakdown vol t age and maxi mum cur r ent speci f i cat i ons ar e not exceeded. However , per f or mance may not be qui t e as good. For power t ypes, make sur e t o use a heat si nk. Hor i zont al out put ( or SMPS) t r ansi st or s - exact r epl acement i s gener al l y best but except f or ver y hi gh per f or mance moni t or s, gener i c HOTs t hat have speci f i cat i ons t hat ar e at l east as good wi l l wor k i n many cases. Make sur e t he r epl acement t r ansi st or has an i nt er nal damper di ode i f t he or i gi nal had one. For t est i ng wi t h a ser i es l i ght bul b, even a t r ansi st or t hat doesn' t qui t e meet speci f i cat i ons shoul d wor k wel l enough ( and not bl ow up) t o enabl e you t o det er mi ne what el se may be f aul t y. The most cr i t i cal paramet er s ar e Vceo/ Vcbo, I c, and Hf e whi ch shoul d al l be at l east equal t o t he or i gi nal t r ansi st or . I have of t en used by f avor i t e BU208D as a t empor ar y subst i t ut e f or ot her HOTs and SMPS ( chopper ) t r ansi st or s. Make sur e you use a heat si nk and t her mal gr ease i n any case - even i f you have t o hang t he assembl y by a cabl e t i e t o make i t f i t . Def l ecti on yokes - i n t he ol d days, par t i cul ar l y f or TVs, al l of t hese wer e qui t e si mi l ar . I t was common t o j ust swap wi t h one t hat f i t physi cal l y and at most need t o adj ust or change a wi dt h coi l . Wi t h hi gh per f or mance mul t i scan moni t or s, t hi s i s no l onger t he case. Somet i mes i t wi l l wor k but ot her t i mes t he power suppl y won' t even be abl e t o come up as a r esul t of t he i mpedance mi smat ch due di f f er ent coi l s and pol e pi ece conf i gur at i ons. I n addi t i on, t her e may be ot her geomet r y cor r ect i on coi l s associ at ed wi t h t he yoke t hat coul d di f f er subst ant i al l y. CRTs - asi de f r om t he i ssues of physi cal si ze and mount i ng, many f act ors need t o be consi der ed. These i ncl ude def l ect i on angl e, neck di amet er , base pi nout , f ocus and scr een vol t age r equi r ement s, pur i t y and conver gence magnet s, et c. Col or CRT r epl acement i s rar el y wort h t he ef f or t i n any case but t r yi ng t o subst i t ut e a di f f er ent CRT i s aski ng f or f r ust r at i on. For monochr ome CRTs, t her e i s l ess var i at i on and t hi s may be wor t h a t r y.