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KEYBOARDS


Keyboards are simple devices controlled by manipulating a matrix of individual electrical switches, which can be entered one at a time to input your desired commands. Although keyboards are simple devices they do however can run into problems here and there.When you multiply this number of moving parts times the 100+ keys on a typical keyboard, you are faced with a substantial number of moving parts. A jam or failure in any one of these many mechanical parts results in a keyboard problem. Most keyboard failures are hardly catastrophic, but they can certainly be inconvenient.

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 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 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. This will loosen and dislodge any larger, heavier foreign matter, and allow it to fall out of the keyboard. A soft-bristled brush will help loosen the debris. Return the keyboard to an upright position. Use a can of compressed air (available from almost any electronics or photography store) to blow out the remainder of foreign matter. Because this tends to blow 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 help loosen any stubborn debris. Now that the keyboard is cleaned out, squirt a small amount of good-quality electronics-grade 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 keyboard again before reinstalling the key caps. If the problems persist, the keyboard might be damaged or the individual key(s) might simply be worn out beyond recovery. In such an event, replace the keyboard outright.

Keyboard Q & A

Why during initialization, an error message indicates that no keyboard is connected?
Check your keyboard cable and see that it is inserted properly and completely into the PC connector. Remember that you will have to reboot your system to clear this error message. Try another compatible keyboard. If a new keyboard assembly works properly, there is probably a wiring fault in the 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 operational. If so, your trouble now lies in the PC. Check the wiring between the PC keyboard connector and the 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 want to check the soldering connections where the keyboard connector attaches to the motherboard.

Why during initialization, an error message indicates that the keyboard lock is on?
In many cases, the detection of a locked keyboard will halt system 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 circuit. In the opposing position, the switch 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, there is probably a logic fault on the motherboard (perhaps the keyboard controller). Your best course is to try another motherboard.

Why is my keyboard completely dead—no keys appear to function at all?
All other computer operations are normal. In this symptom, it is assumed 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 LED's might not be working properly. Your first step in such a situation is to try a known-good keyboard in the system. Notice that you should reboot the system when a keyboard is replaced. If a known-good keyboard works, the fault is probably on the keyboard-interface IC. You can attempt to replace this IC if you wish, but it is often most economical to simply 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 . If the +5-V signal is missing, the female connector might be broken. Check the connector’s soldering junctions on the motherboard. Preheat any connectors that appear fatigued or intermittent. Many motherboards 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 fuse. If problems continue, replace the motherboard.

Why is my keyboard acting erratically?
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 nui-sance to a major headache. Chances are that your key contacts are dirty. Sooner or later, dust and debris works into all key switches. Electrical contacts eventually become coated and fail to make contact reliably. This symptom is typical of older keyboards, or keyboards that have been in service for prolonged periods of time. In many cases, you need only vacuum the keyboard and clean the suspect contacts with a good-quality electronic contact cleaner. Begin by disconnecting the keyboard. Use a static-safe, 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 regularly as preventive 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 their flat ends (just the tips) bent inward. Grasp the key cap and pull up evenly. You can expect the cap to slide off with little 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 cleaner into the switch. Work the switch in and out to distribute the cleaner. Repeat this maintenance once or twice to clean the switch thoroughly. Allow residual cleaner to dry thoroughly before re-testing the keyboard. Never use harsh cleaners or solvents. Industrial-strength chemicals can easily ruin plastic components and housings. Reapply power and retest the system. If the suspect key(s) respond normally again, install the removed key caps and return the system to service. As a preventive 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 neces-sary for you to remove the rubber or plastic boot to clean the PC board contacts. Depending on the design of your particular membrane switch, this might not be an easy task. If you are able to see the contact boot, use a pick or 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 replace the defective key switch(es). Observe the board closely for cracks or fractures. Many key-switch designs still utilize through-hole technology, but you should exercise extreme care when desoldering and resoldering. Extra care helps prevent accidental damage to the PC keyboard. You also have the more economical option of replacing the entire keyboard assembly outright.

Why is my keyboard acting erratically?
One or more keys might be stuck or repeating. Suspect a shorted or jammed key. Short circuits can be caused by conductive foreign objects (e.g., staples, paper clips) falling into the keyboard and landing across PC board contacts. Remove all power and disassemble the keyboard housing assembly. Once the keyboard is exposed, shake out the 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 cleaners to the key, and work the key in and out to distribute cleaner evenly. If the key returns to normal, you can reassemble the computer and return it to service. Keys that remain jammed should be replaced. If you can not clear the jammed key, simply replace the entire keyboard 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.

Why are my keyboard keys not functioning as expected?
Pressing a key causes unexpected results or a series of operations that would ordinarily not 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 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 light should stop blinking). Press the and keys while pressing

—this will clear all of the keyboard’s programming. 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.

Why does my wireless keyboard types random characters?
You’ll need to reset both ends of the wireless system. First, take a look at the DIP 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 and receiver are both set for the same channel. Find the “Reset” button on both the transmitter and receiver. Press the RF receiver reset button first, then press the RF transmitter button immediately after (usually within 15 seconds of one another). If the problem persists, reboot the system and try the reset process again.

Why is it that my wireless keyboard beeps while 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.

Why when I type characters do not appear, but the cursor moves?
This issue is a result of the color scheme being used. Check the color scheme selected by right clicking on the desktop. Click on Properties, then the Appearance tab. Set the scheme to Windows standard. Click on OK to return to the desktop. The text should now appear normal. This solution can generally be attempted with any application.

Why is it that some function keys and Windows keys don't work as they are supposed too?
For example, this is a known problem with Toshiba 8500 desktop systems and the Microsoft Natural Keyboard. In virtually all cases (including the 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 keys. You’ll need to try a generic keyboard or upgrade the system’s keyboard controller BIOS.

Why is it that one or more Windows-specific keys don’t work?
This is almost always a limitation of the keyboard-controller BIOS. For example, a Jetkey keyboard controller BIOS (v.3.0) will not recognize the right Windows key on a Microsoft Natural Keyboard. You’ll need to try a generic keyboard or upgrade the system’s keyboard- controller BIOS.

Why is it that the NumLock feature might not 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:
1 Click Start, select Settings, then click Control panel.
2 Doubleclick the System icon and select the Device manager tab.
3 Doubleclick the Ports entry to expand it.
4 Doubleclick the port to which the pen (or touch-screen) device is connected.
5 In the Device usage area on the General tab, click the Original configuration (current) check box to clear it (if you’re using OSR2, click the Disable in this hardware profile check box to select it).
6 Click OK, then restart the system when prompted.



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