Most of the circuitry associated with the computers 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 6 short beeps is produced during boot up.
* Wrong characters display.
* An IBM compatible 301 error code displays.
Basic Keyboard Checks
Keyboard information is stored in the CMOS setup memory, and must accurately reflect the configuration of the system; otherwise, an error occurs. In most CMOS screens, the setup information includes keyboard enabling, Numlock key condition at startup, typematic rate, and typematic delay. The typematic information applies to the keyboars capability to repeat characters when the key is held down. The typematic rate determines how quickly characters are repeated, and the delay time defines the amount of time the key can be held before typematic action occurs. A typical typematic rate setting is 6 characters per second; the delay is normally set at 250 milliseconds.
As with other components, the only time a configuration problem is likely to occur is when the system is being set up for the first time or when a new option is installed. The other condition that cusses a configuration problem involves the system boards CMOS backup battery. If the battery fails, or has been changed, the contents of the CMOS setup will be lost. After replacing the battery, you must always run the setup utility to reconfigure the system.
Turn on the system and observe the BIOS screens as the system boots up. Note the keyboard type listed in the BIOS summary table. If possible, run a selected diagnostic program to test the keyboard. Run the programs keyboard test function, and perform the equivalent of the All test function if available. These test are normally very good at testing the keyboard for general operation and sticking keys.
If the keyboard produces odd characters on the display, check the windows keyboard settings in the control panel 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 panels keyboard icon.
Keyboard Hardware checks
If you suspect a hardware problem, you must first isolate the keyboard as the definite source of the problem. Because the keyboard is external to the system unit, detachable, and inexpensive, begin by exchanging the keyboard with a good keyboard. If the new keyboard works correctly, return the system to full service and service the defective keyboard appropriately.
To service a defective keyboard remove the back cover of the keyboard and check for the presence of a fuse in the +5v (DC) supply and check it for continuity. 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, Just replace it with a fuse of the same type and rating.
If the system still wont boot up. recheck the CMOS setup to make sure that the keyboard is enabled. Check the keyboard cabling for continuity. And, finally, check the video display system (monitor and adapter card) to make sure that it is functional.
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 6 short beeps is produced during boot up.
* Wrong characters display.
* An IBM compatible 301 error code displays.
Basic Keyboard Checks
Keyboard information is stored in the CMOS setup memory, and must accurately reflect the configuration of the system; otherwise, an error occurs. In most CMOS screens, the setup information includes keyboard enabling, Numlock key condition at startup, typematic rate, and typematic delay. The typematic information applies to the keyboars capability to repeat characters when the key is held down. The typematic rate determines how quickly characters are repeated, and the delay time defines the amount of time the key can be held before typematic action occurs. A typical typematic rate setting is 6 characters per second; the delay is normally set at 250 milliseconds.
As with other components, the only time a configuration problem is likely to occur is when the system is being set up for the first time or when a new option is installed. The other condition that cusses a configuration problem involves the system boards CMOS backup battery. If the battery fails, or has been changed, the contents of the CMOS setup will be lost. After replacing the battery, you must always run the setup utility to reconfigure the system.
Turn on the system and observe the BIOS screens as the system boots up. Note the keyboard type listed in the BIOS summary table. If possible, run a selected diagnostic program to test the keyboard. Run the programs keyboard test function, and perform the equivalent of the All test function if available. These test are normally very good at testing the keyboard for general operation and sticking keys.
If the keyboard produces odd characters on the display, check the windows keyboard settings in the control panel 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 panels keyboard icon.
Keyboard Hardware checks
If you suspect a hardware problem, you must first isolate the keyboard as the definite source of the problem. Because the keyboard is external to the system unit, detachable, and inexpensive, begin by exchanging the keyboard with a good keyboard. If the new keyboard works correctly, return the system to full service and service the defective keyboard appropriately.
To service a defective keyboard remove the back cover of the keyboard and check for the presence of a fuse in the +5v (DC) supply and check it for continuity. 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, Just replace it with a fuse of the same type and rating.
If the system still wont boot up. recheck the CMOS setup to make sure that the keyboard is enabled. Check the keyboard cabling for continuity. And, finally, check the video display system (monitor and adapter card) to make sure that it is functional.
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