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Troubleshooting Keyboards ]
There is an apparent failure of the keyboard
Explanation: The keyboard appears to be bad. You are getting errors at boot time
saying that the keyboard is not attached or has failed, or you are unable to get any
characters to register on the computer.
Diagnosis: This is almost always a configuration or connection problem. It's
extremely rare for a keyboard to fail outright; they're just too simple of a device to
have a lot of failures. A common problem is having the keyboard not inserted fully into
the connector on the motherboard.
Note: Remember to turn off
the PC when switching keyboards. You won't likely damage anything by switching them with
the power on, but the PC might not respond correctly.
- Make sure you do not try boot the PC with a key pressed down on the keyboard. This will
often cause the keyboard to register an error when the PC is started up.
- Keyboards for the original PC/XT used different electrical signaling than the keyboards
used by all AT and later PCs. Most keyboards (except for extremely old ones) have a switch
on the bottom to select between XT and AT mode. Make sure that the switch is set correctly
(normally to AT for all 286, 386 etc. PCs) or the keyboard will not work.
- The simplest thing to try if you suspect a bad keyboard of course is to switch the
keyboard with another one and see if the second one works. If it does, then swap back the
first one. If the first one now works, it was inserted incorrectly before and should now
be OK. If it still doesn't, it is bad and should be repaired or replaced.
- Make sure that the keyboard is inserted fully and completely into its socket on the
motherboard. You may have to rotate the connector to make sure it lines up properly with
the socket, and you may have to wiggle it and apply some pressure to get it entirely into
Warning: Some keyboards can
be difficult to insert into some keyboard sockets, because of variation in the shape of
the connector or the size of the pins. Do not try to force the keyboard into the
socket. The socket is usually mounted directly onto the motherboard at a right angle and
with little support. If you push too hard you may break the connector, which will ruin the
- If you are attempting to run the PC without a keyboard (which is done sometimes for
network servers or in other applications) make sure that you disable the BIOS setting that causes
the PC to halt on a keyboard error.
- Make sure the keyboard cable is not being pulled, stretched or crimped, and that the
point where it attaches to the keyboard is not loose.
- If your PC has an integral PS/2-style mouse port and a mini-keyboard port, these
connectors are the same physical size and shape. Make sure that you don't mix up the
keyboard and mouse ports or neither will work properly. Note that I have seen these two
ports mislabeled on the back of the system case before!
- If you replace the keyboard with another, or if the original keyboard is tested on
another PC and it works there, this implicates either the keyboard controller chip or the
motherboard itself. Troubleshoot the keyboard controller
here or the motherboard here.
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