Keyboards

20 KEYBOARDS

2

S Y S T E M D A T A A N D T R O U B L E S H O O T I N G

CONT CO NTEN ENTS TS AT A GL GLAN ANCE CE Keyboard Construction Key codes Keyboard interfaces

Dvorak Keyboards

Replacing the Preventing the problems Dealing with large objects Dealing with spills Disabling a keyboard

Converting to Dvorak keyboards

Keyboard Key board Troub roubleshooting leshooting Keyboard Cleaning and Maintenance Correcting problem keyboards Vacuum cleaners and keyboards

Further Study

Keyboards (Fig. 20-1) are the classic classic input device.

By manipulating a matrix matrix of individual electrical switches, commands, and instructions can be entered into the computer one character at a time. If you’ve used computers or typewriters to any extent, you already have an excellent grasp of keyboard handling. handling. However, keyboards are not without without their share of drawbacks and limitations. limitations. Although today’s keyboard switches are not mechanically complex, there are a number number of important moving parts. parts. When you multiply this number of moving parts times the 80 to 100+ keys on a typical keyboard, you are faced with a substantial substantial number of moving parts. parts. A jam or failure failure in any one of these many mechanical parts results in a keyboard problem. problem. Most keyboard failures are hardly 663

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FIGU FI GURE RE 20 20-1 -1

A Cherry G83-3000 keyboard.

Cherry Electrical Products

Keycap

Actuator Mechanical contacts

Schematic symbol

Spring

FIGUR FIGURE E 20-2 20-2

A mechanical switch assembly.

catastrophic, but they can certainly be inconvenient. This chapter gives you the information needed to understand and repair computer keyboards.

Keyboard Keyboard Construction Constr uction To understand a keyboard, you must first understand the kinds of switches that are used. In general, you should be concerned with two types of switches: mechanical switches switches and membrane switches. Both switches are used extensively through out the computer industry, but any single keyboard will use only one type of switch. A mechanical key switch is shown in Fig. 20-2. Two tempered bronze contacts are separated by a plastic plastic actuator bar. The bar is pushed up by a spring in the switch base. When the key cap is pressed, the actuator bar bar slides down. This action compresses compresses the spring and allows the gold-plated gold-plated contacts to touch. Because gold is a soft metal metal and an excellent conductor, a good, low-resistance electrical electrical contact is developed. When the key cap is released, the compressed spring expands and drives the plastic actuator bar between the contacts once again. The entire stroke of travel on a mechanical mechanical switch is little more than 3.56 mm (0.140"), but an electrical contact (a make condition) can be established in as little as 1.78 mm (0.070"). Mechanical switches are typically typically quite rugged—many rugged—many are rated for 100 million cycles or more.

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A diagram of a membrane key switch is illustrated illustrated in Fig. 20-3. A plastic actuator rests on top of a soft rubber boot. The inside of the rubber rubber boot is coated with a conductive silver-carbon compound. Beneath the rubber boot are two open PC board contacts. When the key cap is pressed, the plastic plastic actuator collapses the rubber boot. Collapse forces the conductive material across both PC board contacts to complete the switch. When the key cap is released, the the compressed rubber boot breaks its contact on the PC board returns returns to its original shape. The full travel stroke stroke of a membrane key switch is about 3.56 mm (0.140")—roughly the same as a mechanical mechanical switch. An electrical contact is established established in about 2.29 mm (0.090"). (0.090"). Membrane switches are not quite as durable as mechanical switches. Most switches are rated for 20 million cycles or less. Mechanical and membrane switches offer a number of unique advantages and disadvantages. Mechanical switches tend to be highly reliable reliable and provide a good tactile feedback when typing (that “clicking” noise noise we usually associate with offices). offices). On the other hand, mechanical keyboards are more expensive to manufacture, and can be extremely sensitive to spills and foreign matter. Membrane switches are not quite quite as reliable, and tend to offer a softer, “mushier” “mushier” feel when typing (some people people prefer this feel). Because of the membrane cover used in the keyboard, membrane switches seem to withstand spills and foreign matter better than mechanical switches. The next step in understanding a keyboard is to learn about the key matrix. Keys are not interpreted individually—that individually—that is, each switch is not wired directly to the motherboard. Instead, keys are arranged arranged in a matrix of rows rows and columns (Fig. 20-4). When a key is pressed, a unique row (top to bottom) and column (left to right) signal is generated to represent the corresponding key. The great advantage of a matrix approach is that a huge array of keys can be identified using only a few row and and column signals. Wiring from the keyboard is vastly simplified. An 84-key keyboard can be identified using only 12 column signals and 8 row signals. Keycap

Actuator bar

Schematic symbol

Rubber boot Conductive material PC board traces


A membrane switch assembly.

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Column signals Row signals


Key switch

Simplified diagram of a keyboard matrix.

KEY CODES

When a key is pressed, the row and column signals that are generated are interpreted by a keyboard-interface IC (typically (typically located on the keyboard assembly itself). itself). The keyboard interface converts the row and column signals into a single-byte code (called a key code or scan code). code ). Two unique scan codes are are produced during a key-stroke key-stroke cycle. When the key is pressed, a make code byte is sent along to the system. system. When the key is released, released, a break code byte is generated. Both codes are transmitted transmitted to the host computer in a serial fashion. For example, a make code of 1Eh is sent when the “A” key is is pressed. A 9Eh code is sent when the “A” key is subsequently released. released. By using two individual codes, the the computer can determine when a key is held down, or when keys are held in combinations. Just about every key on a keyboard is typematic—that is, it will repeat automatically if it is held down for more than 500 ms or or so. Typematic settings settings can usually be adjusted in the the CMOS advanced settings for your system. Most computers today are prepared for multinational operation. To accommodate the special characters and punctuation used in various different countries, keyboard controllers can be configured to provide scan codes for different languages. Table 20-1 illustrates the make and break codes for conventional keyboards used in the domestic United States. KEYBOARD INTERFACES

Once a key is pressed and the keyboard interface converts the key-matrix signals into a suitable scan code, that code must be transmitted to the KeyBoard the KeyBoard Controller (KBC) on the host computer motherboard. motherboard. Once key data reaches reaches the keyboard controller, controller, it is converted to parallel data by the KBC, which in turn generates an interrupt that forces the system to handle the key. The actual transfer of scan scan codes between the keyboard keyboard and PC is accomplished serially using one of the interfaces shown in Figure 20-5. Notice that three important signals are really in a keyboard interface: the keyboard clock (KBCLOCK), the keyboard data (KBDATA), and the signal ground. Unlike most serial communication, which is asynchronous, the transfer of data from keyboard to controller is

KEYBOARD KEYBOARD CONSTRUCTI CONSTRUCTION ON

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TABLE TAB LE 20-1 STAN STANDAR DARD D SCAN SCAN CODES CODES FOR FOR US KEY KEYBOA BOARDS RDS

KEY

MAKE CODE

BREAK CODE

KE Y

MAKECODE

BREAK CODE

A C E

1E 2E 12

9E AE 92

B D F

30 20 21

B0 A0 A1

G I

22 17

A2 97

H J

23 24

A3 A4

K M

25 32

A5 B2

L N

26 31

A6 B1

O Q S

18 10 1F

98 90 9F

P R T

19 13 14

99 93 94

U W

16 11

96 91

V X

2F 2D

AF AD

Y 0/)

15 0B

95 8B

Z 1/!

2C 02

AC 82

2/@ 4/$ 6/^

03 05 07

83 85 87

3/# 5/% 7/&

04 06 08

84 86 88

8/* ./>

09 29

89 A9

9/( –/_

0A 0C

8A 8C

=/+ ]

0D 1B

8D 9B

[ ;/:

1A 27

9A A7

'/"

28

A8

,/<

33

B3

//?

35

B5

L Sh

2A

AA

L Ctrl

1D

9D

L Alt

38

B8

R Sh R Ctrl

36 E0 1D

B6 E0 9D

R Alt Caps

E0 38 3A

E0 B8 BA

BK SP Space

0E 39

8E B9

Tab Enter

0F 1C

8F 9C

ESC F2

01 3C

81 BC

F1 F3

3B 3D

BB BD

F4 F6 F8

3E 40 42

BE C0 C2

F5 F7 F9

3F 41 43

BF C1 C3

F10 F12

44 58

C4 D8

F11 Up Ar

57 E0 48

D7 E0 C8

Dn Ar Rt Ar

E0 50 E0 4D

E0 D0 E0 CD

Lt Ar Ins

E0 4B E0 52

E0 CB E0 D2

Home Del Pg Dn

E0 47 E0 53 E0 51

E0 C7 E0 D3 E0 D1

Pg Up End ScrLk

E0 49 E0 4F 46

E0 C9 E0 CF C6

* All MAKE and BREAK codes are given in hexidecimal (*hex) values. * Alphabetic characters represent both upper and lower case.

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IBM PC/XT/AT configuration

6 pin mini-DIN connector

3

1

5

6

3

4

5

4

1

2

2 1 2 3 4 5

KBCLOCK KBDATA nc Ground 5 Vdc (or 3.0 or


3.3

Vdc)

1 2 3 4 5 6

KBDATA nc Ground 5 Vdc (or 3.0 or KBCLOCK nc

3.3

Vdc)

Keyboard interface connectors.

accomplished synchronously—data synchronou sly—data bits are returned in sync with the clock signals. As you might expect, the signal ground provides a common reference for the keyboard and system. The keyboard is powered by +5 Vdc, which is also provided through the keyboard interface. It is also important that you notice that most XT-style systems are designed with a unidirectional data path (from keyboard to system). AT-style keyboard interfaces are bi-directional. This feature allows AT keyboards to be controlled and programmed from the PC.

Dvorak Keyboards Most technicians are familiar with QWERTY-style keyboards—this standard format for typewriters was adopted in the late 1800s. A popular alternative to the QWERTY keyboard is the Dvorak the Dvorak keyboard . keyboard . Mechanically and electronically, the Dvorak keyboard is identical to conventional keyboards. keyboards. Only the key order is different—all of the vowels are located on the left side of your home row (the middle row of letter s) in the pattern: AOEUIDHTNS. Dvorak keyboards claim several advantages over QWERTY QWERTY models. Most letters typed (~70%) are on the home row, so finger (and (and wrist strain) can be reduced. reduced. With less reach to deal with, typing can be accomplished faster, faster, and with fewer errors. The vast majority of Dvorak words use both hands for typing, typing, but thousands of words demand one-handed typing for QWERTY keyboards—this keyboards—this spreads out the strain on your hands more evenly. CONVERTING TO DVORAK KEYBOARDS

There are two classic methods of implementing Dvorak keyboards: dedicated keyboards and keyboard and keyboard conversions. conversions. Dedicated keyboards aare re just as the name implies—you implies—you buy a ready-made Dvorak keyboard keyboard and plug it in. Although the keys are located located in different places, the key codes are the same, same, so your PC doesn’t know the difference. difference. As a result, you can interchange QWERTY and Dvorak keyboards at will without any changes to the

KEYBOARD KEYBO ARD CLEAN CLEANING ING AND MAIN MAINTENAN TENANCE CE

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PC or operating system. You can also convert your existing QWERTY QWERTY keyboard to Dvorak under Windows 95: s s s s s

Open the Control panel and panel and doubleclick on the Keyboard the Keyboard icon. icon. Select the Language the Language page page and doubleclick on the English the English (United States) entry (or your own default entry for countries outside of the U.S.). Select United States (Dvorak) from the list that appears. Save your changes—you might need to install a diskette with the proper drivers. It might be necessary to reboot the system.

Under DOS, you will need a DOS TSR to handle the conversion. For MS-DOS 5.0 5.0 through 6.22, you can find the Dvorak TSR on the MS-DOS the MS-DOS Supplemental Disk . You can obtain the driver files from Microsoft’s FTP or Web site ( http://www.microsoft.com ), or from the Microsoft forum on CompuServe (GO (GO MSDOS). Download the file DOS62S.EXE. DOS62S.EXE. If you do download and extract these supplemental DOS files, be very sure to extract them to a new or temporary directory. Under no circumstances should you allow DOS files to overwrite files files in the DOS directory or anywhere in your Windows directories.

Once the software conversion is made, you will need to exchange the keys on your QWERTY keyboard. Figure 20-6 illustrates the comparison comparison between a QWERTY key layout and a Dvorak key layout. You can use a key pulling tool to physically physically exchange the key caps, or use key stickers or overlays from Hooleon Corporation at (602)-634-7515 or Keytime at (206)-522-8973. (206)-522-8973. You can also obtain more more detailed information information directly from Dvorak International at (802)-287-2434.

Keyboard Ke yboard Cleaning and Maintenance Keyboards are perhaps the most abused part of any computer, yet they are often ignored until serious problems develop. develop. With some regular cleaning and maintenance, maintenance, however, a QWERTY -----------Q

W

E

R

T

Y

U

I

O

P

A

S

D

F

G

H

J

K

L

;

Z

X

C

V

B

N

M

,

.

/

'

Dvoark --------“

,

.

P

Y

F

G

C

R

L

/

A

O

E

U

I

D

H

T

N

S

-

;

Q

J

K

X

B

M

W

V

Z


QWERTY vs. Dvorak keyboards.

2


670

KEYBOARDS

keyboard can easily last for the lifetime lifetime of a computer. This part of the chapter shows you some practical techniques for keyboard service. CORRECTING PROBLEM KEYBOARDS

Virtually all computer keyboards are open to the air. Over time, everyday dust, pet hair, air vapor, cigar/cigarette smoke, and debris from hands and ordinary use will settle into the keyboard. Eventually, accumulations of this foreign matter will cause keys to stick, or will prevent keys from making proper prope r contact (i.e., a key does not work every time it is pressed). In either case, keyboard problems will develop. Fortunately, correcting a finicky keyboard is a relatively straightforward process. Start by removing the key caps of the offending keys. Be sure to note where each key is placed before starting your disassembly—especially if the keyboard is a DVORAK-type DVORAK-type or unusual ergonomic design. To remove a key cap, bend an ordinary paper clip into the shape of a narrow “U”, and bend-in small tabs at the tip of the “U” shape. Slip the small tabs under the key cap and pull up gently. Do not struggle with the key cap. If a cap will not come off, remove one or more adjacent caps. If there is a substantial accumulation of foreign matter in the keyboard, you should consider removing all of the key caps for a thorough cleaning, but this requires more time. Avoid removing the unless it is absolutely necessary because the space bar is often much more difficult to replace than ordinary keys.

Flip the keyboard upside down and rap gently on the case. case. This will loosen and dislodge any larger, heavier foreign matter, and allow allow it to fall out of the keyboard. A soft-bristled brush will help help loosen the debris. debris. Return the keyboard keyboard to an upright upright position. Use a can of compressed air (available from almost any electronics or photography store) to blow out the remainder of foreign matter. matter. Because this tends to blow dust dust and debris in all directions, you might wish to use the compressed air outside or in an area away from your workbench. A medium- or firm-bristled brush will will help loosen any stubborn debris. Now that the keyboard is cleaned out, squirt a small amount of good-quality electronicsgrade contact cleaner (also available from almost any electronics store) into each key contact, and work the key to distribute the cleaner evenly. Allow a few minutes for the contact cleaner to dry completely and test the the keyboard again before reinstalling reinstalling the key caps. If the problems persist, the keyboard might be damaged or the individual key(s) might sim ply be worn out beyond recovery. In such an event, replace the keyboard keyboard outright. VACUUM CLEANERS AND KEYBOARDS

There is an ongoing debate as to the safety of vacuum cleaners with computer equipment. The problem is static discharge. discharge. Many vacuum cleaners—especially cleaners—especially small, inexpensive inexpensive models—use cheap plastic and synthetic synthetic fabrics in their construction. When a fast air flow passes over those materials, a static charge is developed (just like combing your hair with a plastic comb). If the charged vacuum touches touches the keyboard, a static static discharge might have enough potential to damage the keyboard-controller IC, or even travel back into the motherboard for more serious damage.

KEYBOARD KEYBOARD CLEANING CLEANING AND MAINTENAN MAINTENANCE CE

FIGURE FIGURE 20-7 20-7

671

A Curtis anti-static keyboard mat. Curtis, a division of Rolodex, Secaucus, NJ 07094

If you do choose to use a vacuum for keyboard cleaning, take these two steps to prevent damage. First, be sure that the the computer is powered down and disconnect disconnect the keyboard from the computer before starting starting service. If a static discharge does occur, the the most that would be damaged is the keyboard itself. Second, use a vacuum cleaner that is made for electronics work and certified certified as “static-safe.” “static-safe.” Third, try working on an anti-static anti-static mat (such as the mat in Fig. 20-7), which is properly grounded. This will tend to “bleed-off” static charges before they can enter the keyboard or PC. REPLACING THE

Of all the keys on the keyboard, replacing the is probably the most difficult. The is kept even by a metal wire that is inserted into slots on each leg of the plastic bar key. However, you have to get the wire into the slots without pressing pressing the wire. If you push the wire down, you compress the wire and installation becomes impossible. As a general rule, do not remove the Bar> unless absolutely necessary. If you must remove the , Bar>, remove several surrounding key caps also. also. This will let you get some tools under the wire later on. Once the is re-inserted, you can easily replace any of the other key caps. PREVENTING THE PROBLEMS

Keyboard problems do not happen suddenly (unless the keyboard is dropped or physically abused). The accumulation of dust and debris is is a slow process that can take months months (sometimes years) to produce produce serious, repetitive keyboard problems. problems. By following a regimen of regular cleaning, you can stop problems before they manifest themselves in your keyboard. In normal office environments, environments, keyboards should should be cleaned once every four four months. Keyboards in home environments environments should be cleaned every two months. Key boards in harsh or industrial environments should be cleaned even more frequently. Turn your keyboard upside-down and use a soft-bristled brush to clean between the keys. This prevents debris debris that might already be on the keys keys from entering the keyboard. keyboard. Next, run the long, thin nozzle of your compressed air can between the key spaces to blow

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K E Y BO A R D S

out any accumulations of dust. dust. Because compressed air air will tend to blow dust dust in all directions, you might consider “blowing down” the keyboard outside, or in an area away from your workbench. Instead of compressed air, you might use a “static-safe” “static-safe” vacuum cleaner to remove dust and debris. DEALING WITH LARGE OBJECTS

Staples and paper clips pose a clear and present danger to keyboards. keyboards. Although the odds of a staple or paper clip finding its way into a keyboard are generally slight, foreign objects can jam the key or short it out. If the keyboard is moved, the object can wind up in the key board’s circuitry where serious serious damage can occur. When a foreign object falls into into the keyboard, do not move the keyboard. Power down the PC, then then locate the object and find the nearest key. Use a paper clip bent in a “U” shape shape with the ends of the “U” angled angled inward to remove the nearest key cap. Use a pair of non-conductive tweezers tweezers or needle-nose pliers to remove remove the object. Replace the key cap. cap. DEALING WITH SPILLS

Accidental spills are probably probably the most serious and dangerous keyboard problem. Coffee, soda pop, and even tap water is highly conductive (even corrosive). corrosive). Your keyboard will almost certainly short circuit. circuit. Immediately shut down your computer computer (you might be able to exit your application using using a mouse) and disconnect the keyboard. keyboard. The popular tactic is to simply let the liquid dry. The problem with this tactic is that most liquids liquids contain minerals and materials that are corrosive to metals—your keyboard will never be the same unless the offending liquid is removed removed before it dries. Also, liquids tend to turn any dust and smoke film into a sticky glue that will just jam the keys when dry (not even considering the sticky sugar in most soda pop). Disassemble the keyboard’s main housings and remove the keyboard printed-circuit assembly. As quickly as you can after the incident, rinse the the assembly thoroughly in clean, room-temperature, de-mineralized water (available from any pharmacy for contact lens maintenance). You can clean the plastic housings separately. Do not use tap water. Let the assembly drip dry in air. Do not attempt to accelerate the drying process with a hair dryer or other such heat source. The de-mineralized water should dry clean without without mineral deposits or any sticky, conductive residue. Once the assembly is dry, you might wish to squirt a small amount of good-quality, electronics-grade contact clea ner into each key switch to ensure that no residue is on the contacts. Assuming that the keyboard’s circuitry was not damaged by the initial spill, you should be able to reassemble the keyboard and continue con tinue using it without problems. If the keyboard behaves erratically (or not at all), replace the keyboard outright. DISABLING A KEYBOARD

Keyboards are an essential essential peripheral for all computers, computers, except servers. In many cases, network administrators would prefer to restrict direct access to the server, and prevent potential tampering. Traditional PCs did not allow you disable the keyboard, but newer systems do offer a CMOS setup entry entry that can enable or disable the keyboard. When the keyboard is disabled through CMOS, the PC will boot without suffering “Keyboard not found” errors. Before starting service on a server, it might be necessary to reattach reattach and reenable the keyboard.

KEYBOARD TROUBLESHOOTING

673

Keyboard Troubleshooting Although their appearance might seem daunting at first glance , keyboard systems are not terribly difficult to troubleshoot. This ease is primarily primarily because of the keyboard’s modularmodularity—if all else fails, it’s a simple simple matter to replace a keyboard outright. The keyboard’s great weakness, however, is its vulnerability to the elements. Spills, dust, and any other foreign matter that finds its way between the key caps can easily ruin a keyboard. The keyboard’s PC board is also a likely candidate to be damaged by impacts or other physical abuse. The following procedures address many of the most troublesome keyboard problems. You can use the SCODE22.ZIP utility on the Companion CD to examine the scan codes for each key. You can use this utility to to determine which keys (if any) are not working. Symptom 20-1. During initialization Symptom initialization,, an error error message message indicates indicates that no keyboard is connected Check your keyboard cable and see that it is inserted prop-

erly and completely into into the PC connector. Remember that you will will have to reboot your system to clear clear this error message. Try another compatible compatible keyboard. If a new keyboard keyboard assembly works properly, properly, there is probably a wiring fault in the original original keyboard. Given the very low price of new keyboards, it is usually most economical to simply replace a defective keyboard. If you’re working on a file or network server, see that the CMOS setup has enabled the keyboard. If a known-good keyboard fails to function, try the original keyboard on a known-good PC to verify that the keyboard itself is indeed indeed operational. If so, your trouble now lies in the PC. Check the wiring between between the PC keyboard connector and the motherboard. motherboard. Check the connector pins to be sure that none of them have been bent or pushed in (resulting in a bad connection). You might also also want to check the the soldering connections connections where the keyboard keyboard connector attaches to the the motherboard. Repeated removals and and insertions of the keyboard might have fatigued the the solder joints. Reheat any defective solder solder joints. If the keyboard connector is intact, it is likely likely that the keyboard controller IC (KBC) (KBC) has failed. Try booting the PC with a POST board board installed (as covered in Chapter 15). A KBC failure will usually usually be indicated by the system stopping on the appropriate POST code. You can attempt to replace the KBC or replace the motherboard outright. outright. If a POST board indicates a fault other than than a KBC (such as the programmable interrupt controller, which manages the KBC’s interrupt), you can attempt to replace that component, or simply exchange the motherboard anyway. Symptom 20-2. During initiali Symptom initialization, zation, an error messag message e indicates indicates that that the keyboard lock is on In many cases, the detection of a locked keyboard will halt sys-

tem initialization. Be sure that the keyboard lock switch is set completely to the “unlocked” position. If the switch is unlocked, but the system detects it as locked. The switch might be defective. Turn off and unplug the system, then use a multimeter to measure continuity across the lock switch (you might need to disconnect the lock switch cable from the motherboard. In one position, the switch should measure as an open open circuit. In the opposing position, the switch should should measure as a short circuit. If this is not the case, the lock switch is probably bad and should be replaced. If the switch measures properly, properly, there is probably a logic fault on the motherboard (perhaps (perhaps the keyboard controller). Your best course is to try another motherboard.

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Symptom 20-3. The keyboard keyboard is completel completely y dead—no dead—no keys keys appear to function at all All other computer operations operations are normal. In this symptom, it is asas-

sumed that your computer initializes and boots to its DOS prompt or other operating system as expected, but the keyboard does not respond when touched. Keyboard-status LEDs LEDs might not be working properly. properly. Your first step in such such a situation is to try a known-good known-good keyboard in the system. Notice that you should reboot the system system when a keyboard is re placed. If a known-good keyboard works, the fault fault is probably on the keyboard-interface keyboard-interface IC. You can attempt to replace this IC if you wish, but it is often most economical economical to sim ply replace the keyboard outright. If another keyboard fails to correct the problem, use a multimeter and check the +5-V supply at the keyboard connector (refer (refer to Fig. 20-5). If the +5-V signal is missing, missing, the female connector might be broken. Check the connector’s connector’s soldering junctions junctions on the motherboard. Reheat any connectors that appear fatigued or intermittent. intermittent. Many mother boards also use a “pico-fuse” to protect the +5-V supply feeding the keyboard connector. If your +5 V is lost, locate and check the keyboard-connector keyboard-connector fuse. If problems continue, replace the motherboard. Symptom Symptom 20-4 20-4..

The keyb keyboard oard is is acting acting errati erraticall cally y One or more keys appear to

work intermittently, or it is inoperative. The computer operates normally and most keys work just fine, but one or more keys do not respond when pressed. Extra force or repeated strikes might be needed to operate the key. This type of problem can usually range from a minor nuisance to a major headache. Chances are that your key contacts contacts are dirty. Sooner or later, dust and debris works into all key switches. Electrical contacts eventually eventually become coated and fail to make contact reliably. This symptom is typical of older keyboards, keyboards, or keyboards that have been in service for prolonged periods of time. In many cases, you need only vacuum the key board and clean the suspect contacts with a good-quality electronic contact cleaner. Begin by disconnecting the keyboard. Use a static-safe, fine-tipped fine-tipped vacuum to remove any accumulations of dust or debris that might have accumulated on the keyboard PC board. You might wish to vacuum your keyboard keyboard regularly as preventive maintenance. maintenance. Once the keyboard is clean, gently remove the plastic key cap from the offending key(s). The use of a keycap-removal tool is highly recommended, but you might also use a modified set of blunt-ended tweezers with with their flat ends (just the tips) bent inward. Grasp the key cap and pull up evenly. evenly. You can expect the cap cap to slide off with with little resistance. resistance. Do not rip the key cap off—you stand a good chance of marring the cap and causing permanent key switch damage. Use a can of good-quality electronics-grade contact cleaner and spray a little bit of cleaner into the switch assembly. When spraying, attach the long, narrow tube to the spray nozzle—this directs directs cleaner into the switch. switch. Work the switch in and out to to distribute the cleaner. Repeat this maintenance once or twice to clean the the switch thoroughly. Allow residual cleaner to dry thoroughly before before re-testing the keyboard. Never use harsh cleaners or solvents. Industrial-strength Industrial-strength chemicals can easily ruin plastic components components and housings. Reapply power and retest the system. If the suspect key(s) respond normally normally again, install the removed key caps and and return the system to service. service. As a preventive measure, measure, you might wish to go through the process of cleaning every key. Membrane keys must be cleaned somewhat differently from mechanical keys. It is necessary for you to remove the rubber or plastic boot to clean the PC board contacts. Depending on the design of your particular membrane membrane switch, this might not be an easy task. If you are


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able to see the contact boot, use a pick or tweezers tweezers to gently lift the boot. Spray a bit of cleaner under the boot, then work the key to distribute the cleaner. If the boot is confined within the individual key, you might have to remove the suspect key before applying cleaner. If cleaning does not work, your next step should be to disassemble the keyboard and re place the defective key switch(es). switch(es). Observe the board closely for cracks cracks or fractures. Many key-switch designs still utilize through-hole technology, but you should exercise extreme care when desoldering desoldering and resoldering. Extra care helps prevent accidental accidental damage to the PC keyboard. keyboard. You also have the more more economical option of replacing replacing the entire keyboard assembly outright. Symptom Symptom 20-5 20-5.. The keybo keyboard ard is acting acting erratic erratically ally One or more keys might be stuck or repeating. Suspect a shorted or jammed jammed key. Short circuits can be be caused by conductive foreign objects (e.g., staples, paper clips) falling into the keyboard and landing across PC board contacts. contacts. Remove all power and and disassemble the keyboard keyboard housing assembly. Once the keyboard is exposed, shake out the foreign foreign object or remove it with a pair of long needle-nose pliers or sharp tweezers. Accumulations of dirt or debris can work into the key actuator shaft and restrict its movement. Apply good-quality electronics-grade electronics-grade cleaners to the key, and work the key in and out to distribute cleaner evenly. evenly. If the key returns to normal, you can re-assemble re-assemble the computer and return return it to service. Keys that remain remain jammed should be replaced. replaced. If you can not clear the jammed key, simply simply replace the entire keyboard assembly assembly outright. If you elect to replace the keyboard assembly, retain the old assembly for parts—key caps, good switches, and cable assemblies can be scavenged for use in future repairs. Symptom Symptom 20-6. A “KBC “KBC Error” Error” (or similar) similar) is displayed displayed during during system system startup When your computer initializes (either from a warm or cold start) it executes a

comprehensive self-test routine that checks the key ICs in the system (e.g., the CPU, memory, drive controllers, and so on). As part of this power-on self-test (POST) (POST) routine, the computer looks for the KBCLK signal, along with a series of test scan codes generated by the KB controller IC—you can see the keyboard LEDs flash as the controller sequences through its codes. If either the keyboard clock or keyboard keyboard data signals are missing, missing, the POST knows that either the keyboard is disconnected or that the keyboard controller has failed. If you are using a POST board, it will probably probably be displaying a code corresponding to a KBC error. Unless you have the tools and inclination to replace a KBC controller IC, your best course is simply to replace the motherboard outright. Symptom Symptom 20-7. 20-7. Macros cannot be cleared cleared from from a programmable programmable keykeyboard In most cases, you need to use the right key combination to clear the macros. If the

keyboard has a key, press that first (a Program (a Program light or other LED will start blinking). Press the key twice to map the key to itself. Press twice twice to map the key to to itself. Press the key (the Program (the Program light should stop blinking). Press the and keys while pressing —this will clear all of the key board’s programming. The key sequence used for your keyboard might be different, different, so be sure to check the procedure for your own keyboard. If problems persist, replace the keyboard. Symptom Symptom 20-8. 20-8.

The keyboard keyboard keys are not not functioning functioning as expected expected

Pressing a key causes unexpected results or a series of operations that would ordinarily not

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be attributed to that key. Chances are that the keyboard has been programmed with macros, and you’ll need to clear those macros to restore normal keyboard operation. If the keyboard has a key, press that first (a Program (a Program light or other LED will start blinking). Press the key twice to map the key to itself. Press twice to map the key to itself. Press the key (the Program (the Program light should stop blinking). Press the and keys while pressing —this will clear all of the keyboard’s pro gramming. The key sequence used for your keyboard might be different, so be sure to check the procedure for your own keyboard. If problems persist, replace the keyboard. Symptom 20-9. Some keys on a programma programmable ble keyboard keyboard will not remap remap to their default state This can happen with some Gateway 2000 (AnyKey) key-

boards—as well as other programmable keyboards—and you might have to “force clear” the keyboard at boot time. Power down the system. While holding holding down the key, turn the system power back on. Continue booting with the key pressed until the Program the Program light (or similar LED) LED) quits flashing. This light will stay lit until you press and release it. For Gateway 2000 AnyKey keyboards, if there is an “AnykeyXX T” line in the AUTOEXEC.BAT file, this will terminate any programming programming function of the keyboard. If there is an “AnykeyXX A” line in the AUTOEXEC.BAT file, this will activate the programming function. A wireless wireless keyboar keyboard d types types random characte characters rs You’ll need to reset both ends of the wireless system. system. First, take a look at the DIP switch switch settings that control the RF channel for the wireless transmitter and receiver (usually under the battery cover at the keyboard). Be sure that the transmitter transmitter and receiver are both set for the same channel. Find the “Reset” “Reset” button on both the transmitter transmitter and receiver. receiver. Press the RF receiver reset button first, then press the RF transmitter button immediately after (usually within 15 seconds of one another). another). If the problem persists, persists, reboot the system and try try the reset process again. Symptom 20-10.

The wirel wireless ess keybo keyboard ard beeps beeps while while typing typing In virtually all cases, the batteries in the wireless keyboard are running low. Replace the batteries and try the wireless keyboard again—the beeping should stop. Symptom Sym ptom 20-11 20-11..

Symptom 20-12.

Typed character characters s do not appear, appear, but but the cursor moves

This issue is a result of the color scheme being used. Some of the applications reported reported as suffering this problem are MSWORKS 4.0, CASHGRAF, MSBOB (address book and letter writer), and MSPUBLISHER. MSPUBLISHER. Check the color scheme selected by right clicking on the desktop. Click on on Properties Properties,, then the Appearance the Appearance tab. Set the scheme to Windows standard . Click on OK OK to to return to the desktop. The text should should now appear normal. This solution can generally be attempted with any application. Symptom 20-13. Some function function keys and Windows Windows keys might not not work some PC configurations For example, this is a known problem with Toshiba 8500

desktop systems and the Microsoft Natural Keyboard. Keyboard. In virtually all cases (including the


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Toshiba 8500), the PC keyboard controller BIOS recognizes the keyboard during the Power-On Self Test (POST) , but it does not recognize some of the keys—including certain function keys and Windows-specific Windows-specific keys. You’ll need to try a generic keyboard or upgrade the system’s keyboard controller BIOS. Symptom Symptom 20-14. 20-14. One or or more more Windows-s Windows-specific pecific keys don’t work This is almost always a limitation limitation of the keyboard-controller BIOS. BIOS. For example, a Jetkey key board controller BIOS (v.3.0) will not recognize the right Windows key on a Microsoft Natural Keyboard. Keyboard. You’ll need to try a generic keyboard or upgrade upgrade the system’s key board-controller BIOS. Symptom Symptom 20-15. 20-15. Remote-control Remote-control programs don’t work after installing installing keyboard drivers Many PC “remote-control” programs (e.g., PC Anywhere, Rea-

chOut, and Carbon Copy) use keyboard and mouse drivers that are simply not compatible with the keyboard’s specific drivers. For example, the remote-control programs listed will not work when IntelliType software is installed for the Microsoft Natural Keyboard. You’ll need to disable the remote-control software, install patches for the remote-control software that will properly support the keyboard or replace the keyboard with a more generic model. Symptom Symptom 20-16. 20-16. On a PS/2 system, system, you encounter encounter keyboard keyboard errors, errors, even even though the keyboard driver loads successfully Often, you’ll see an error like:

“Keyboard error: keyboard keyboard not found,” and you cannot access the the keyboard. This type of problem is known to occur on PS/2 systems when the IBM ROM BIOS patch file (DASDDRVR.SYS) DDRVR.SYS) is loaded after the keyboard driver in CONFIG.SYS. Rearrange the CONFIG.SYS file file to load the DASDDRVR.SYS DASDDRVR.SYS file before the keyboard driver. Be sure that you are loading the patch driver (DASDDRVR.SYS) that is designed for your specific computer (for example, you cannot use the DASDDRVR.SYS DASDDRVR.SYS file that ships with an IBM PS/2 Model 80 on a PS/2 Model 70 computer). This device driver can normally be found on the SETUP disk that you received received with your IBM PS/2. Otherwise, you can obtain it from IBM (http://www.ibm.com). Symptom Symptom 20-1 20-17. 7.

Assign Assigned ed key sound sounds s do not work work When you assign sounds

to keystrokes (under the Options tab in the Keyboard tool in your Control panel ), ), the sounds might play when you press the assigned keys. This problem is known to occur with some programmable keyboards when HiJaak Pro or HiJaak 95 Graphics Suite installed on your computer. These products might load a device driver named “Runner” that disables disables programmable keyboard sounds. sounds. You might be able to work around the problem by closing the “Runner” task: s s

Press ++ ++ to open the Close program dialog box. If “Runner” is listed, click Runner, Runner, then click End End task .

Symptom 20-18. You cannot use Windows-specific Windows-specific keys to start start task task switching software other than TASKSW16.EXE You can start the desired task

switching software using +, +, or by doubleclicking the desktop. Chances are that your Windows-specific key will not start any other task switching utility if

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TASKSW16.EXE can be found on the path. You’ll need to update the task switching program reference in SYSTEM.INI. SYSTEM.INI. Load SYSTEM.INI SYSTEM.INI into any text editor, and modify the line that reads: TASKMAN=TASKSW16.EXE

to read TASKMAN=

where is the name of the executable file that you want to start when you press the Windows key. Rename the TASKSW16.EXE TASKSW16.EXE file (e.g., TASKSW16.OLD TASKSW16.OLD)) or move it to a directory that is is not in the path. Save and close the SYSTEM.INI SYSTEM.INI file, file, then restart the computer. Symptom 20-19. The NumLock feature might not activate activate when the NumLock key is pressed This can happen with some programmable keyboards when

pen software is installed on the system. You should be able to correct the problem by disabling the pen device: Click Start , select Settings Click Start Settings,, then click Control click Control panel . Doubleclick the System icon and select the Device the Device manager tab. Doubleclick the Ports the Ports entry to expand it. Doubleclick the port to which the pen (or touch-screen) device is connected. In the Device the Device usage area on the General General tab, tab, click the Original configuration (current) check box to clear it (if you’re using OSR2, click the Disable the Disable in this hardware profile check box to select it). 6 Click Click OK OK , then restart the system when prompted. 1 2 3 4 5

To enable your pen device again, repeat these steps, but re-select (or re-clear) the check box in step 5.

Further Study That’s all for Chapter Chapter 20. Be sure to review the glossary glossary and chapter questions on on the accompanying CD. If you have access to the Internet, take a look at some some of the keyboard resources listed: NMB Technologies: http://www.nmbtech.com/ Keytronic: http://www.keytronic.com Mitsumi: http://www.mitsumi.com Microsoft: http://www.microsoft.com http://www.microsoft.com/products/prodref/310_ov.htm /products/prodref/310_ov.htm (Natural Keyboard) Chicony: http://www.chicony.com/

Keyboards

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