MUST READ FOR ALL USERS OF COMPUTER SYSTEMS: HOW TO TROUBLESHOOT YOUR COMPUTER HARDWARE COMPONENTS (KEYBOARD)

When a computer system fails, there are generally two possible causes— hardware or software. Numerous symptoms and problem sources are presented for each of these components. Technicians need to be aware of the different symptoms produced by these devices so that they can move through the diagnostic and repair processes in the most efficient manner possible.

As a technician, you should be able to identify common symptoms and problems associated with each hardware module and know how to isolate, troubleshoot, and repair the problems. I continue to discuss troubleshooting various hardware components of the computer system.

TROUBLESHOOTING KEYBOARD PROBLEMS

Most of the circuitry associated with the computer’s keyboard is contained in the keyboard itself. However, some keyboard interface circuitry is located on the system board. Therefore, the steps required to isolate keyboard problems are usually confined to the keyboard, its connecting cable, and the system board. This arrangement makes isolating keyboard problems relatively easy. Just check the keyboard and the system board.

Keyboard Symptoms

Typical symptoms associated with keyboard failures include the following:

·         No characters appear onscreen when entered from the keyboard.

·         Some keys work, whereas others do not work.

·         A “Keyboard Is Locked—Unlock It” error displays.

·         A “Keyboard Error—Keyboard Test Failure” error displays.

·         A “KB/Interface Error—Keyboard Test Failure” error displays.

·         An error code of six short beeps is produced during bootup.

·         Wrong characters are displayed.

·         An IBM-compatible 301 error code displays.

·         Unplugged keyboard error.

·         Stuck key.

Basic Keyboard Checks

The keys of the keyboard can wear out over time. This can result in keys that don’t make good contact (no character is produced when the key is pushed) or one that remains in contact (sticks) even when pressure is removed. The stuck key will produce an error message when the system detects it. However, it has no way of detecting an open key. If you detect a stuck key, or keys, you can desolder from the keyboard and replace the individual key switches with a good key from a manufacturer or a similar keyboard. However, the amount of time spent repairing a keyboard quickly drives the cost of the repair beyond the cost of a new unit.

An unplugged keyboard, or one with a bad signal cable will also produce a keyboard error message during startup. Ironically, this condition might produce a configuration error message that says “Press F1 to continue.”

If the keyboard produces odd characters on the display, check the Windows keyboard settings in the Control Panel’s Device Manager.

If the keyboard is not installed or is incorrect, install the correct keyboard type. Also, make certain that you have the correct language setting specified under the Control Panel’s keyboard icon.

Keyboard Hardware Checks

If you suspect a keyboard hardware problem, you must first isolate the keyboard as the definite source of the problem (a fairly easy task). Because the keyboard is external to the system unit, is detachable, and is inexpensive, simply exchange it with a known good keyboard.

If the new keyboard works correctly, return the system to full service and service the defective keyboard appropriately. Remove the back cover from the keyboard, check for the presence of a fuse in the +5V dc supply, and check it for continuity. Neither the standard 5-pin DIN nor the 6-pin PS/2 mini-DIN keyboards can be hot swapped.

Disconnecting or plugging in a keyboard with this type of fuse while power is on can cause it to fail. If the fuse is present, simply replace it with a fuse of the same type and rating.

If replacing the keyboard does not correct the problem and no configuration or software reason is apparent, the next step is to troubleshoot the keyboard receiver section of the system board. On most modern system boards, this ultimately involves replacing the system board with another one.

Check in for more post on how to troubleshoot your mouse.