Model M (IBM classic) keyboard stopped working on XP


E

Experimenter2

One day some months ago, I did a routine re-boot, and when Windows XP came
up, I got a continuous beep that told me there was a problem with the
keyboard. The keyboard, a classic IBM MOdel M ("clicky") device, had been
working fine before I re-booted. I've tried 3 separate keyboards, all of
which work well on another machine, and now my XP machine will not recognize
one of them!

Anyone have any suggestions or clues as to what the problem might be? Tnx.
 
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M

Malke

Experimenter2 said:
One day some months ago, I did a routine re-boot, and when Windows XP came
up, I got a continuous beep that told me there was a problem with the
keyboard. The keyboard, a classic IBM MOdel M ("clicky") device, had been
working fine before I re-booted. I've tried 3 separate keyboards, all of
which work well on another machine, and now my XP machine will not
recognize one of them!

Are all the keyboards you tried ps/2 (small round connector)? If yes, try a
USB keyboard. Your ps/2 keyboard port may have failed.

Malke
 
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P

Paul

Malke said:
Are all the keyboards you tried ps/2 (small round connector)? If yes, try a
USB keyboard. Your ps/2 keyboard port may have failed.

Malke

Some other things you can check, if the keyboard is PS/2 are, the fuse
in the keyboard circuit, and jumpers if present.

Some motherboards have a 1x3 set of header pins, and a jumper sits
on two of the pins. That is a "selector", which allows the keyboard
to be run from +5V or +5VSB. The latter choice is used, when the keyboard
is able to "wake" the computer. If someone pulls the jumper plug and
walks off with it, the keyboard/mouse would no longer have power. So
checking the jumper is one thing to do on an older computer.

Right after the jumper, there can be a Polyfuse. That is a type of fuse
which is self-healing. It may cut off the current at around the 1 amp level
or so. Since the fuse is self-healing, it should automatically start
conducting again, once any overload is removed.

If either of those items exist, they may affect the operation of the
keyboard.

On more modern computers, they've removed that jumper choice, so that
the keyboard always runs from +5VSB. On one cheap motherboard I noticed
recently, the Polyfuse is shared by a whole bunch of motherboard circuits,
so if the fuse has a problem, a bunch of stuff fails at the same time.
On older computers, there are multiple Polyfuses, one per pair of USB
headers, one for parallel port and keyboard/mouse perhaps, so if there
is a problem with one of the fuses, it affects fewer things.

The PS/2 has CLOCK and DATA pins, and that is how it communicates.
Hot-plugging a PS/2 device (insert or remove plug with power on), is
not good for the interface, and has been known to damage the interface
circuits.

You can also eyeball the miniDIN connector, for bent or broken bits.
If someone pulled on the cable at some point, there might have been
some damage to the connector.

Paul
 

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