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IBM Model M - Need help troubleshooting ... (PC just keeps beeping)

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sofakng:
I've received a used IBM Model M (1391401) and I completely cleaned all of the keycaps and stems and made sure it was absolutely 100% dry.

When the PC boots, the NUMLOCK is correctly illuminated, but then the PC keeps beeping and displays Keyboard Error and nothing works on the keyboard.

I've cleaned the ribbon cables inside the keyboard (with isopropyl alcohol and Deoxit) but it didn't help.  I'm not sure if the membrane is broken and I was hoping not to remove the rivets but I'm not sure if the problem is the membrane or the PCB.

Can anybody help me diagnose this?

Tactile:
Is it plugged directly into a real PS/2 port or are you using some type of a converter? Is this "keyboard error" message from the BIOS or the operating system?

sofakng:
I'm using a real PS/2 port (on an older Pentium PC).  The keyboard error is coming from the BIOS.

If I unplug the 16-pin ribbon cable the beeping stops.  (ie. I can leave the 8 pin and 4 pin ribbon cables inserted)

Tactile:
Here's an interesting bit of trivia for you: The num-lock LED is controlled by the computer, not the keyboard. When you press num-lock it sends a signal to the computer/OS.requesting different keyboard behavior. If the OS understands then the OS sends a signal to turn the num-lock LED on.

The point of all of this is that the keyboard isn't completely dead or the BIOS wouldn't be able to light that LED. In some BIOSs there is a setting to tell it to ignore keyboard errors - you might check to see if you have that option. The problem might be simply that this old keyboard draws more power than the BIOS expects, causing it to raise a fuss. Model M boards are pretty notorious for this power issue. Some computers don't care while others don't like the power draw. Also, there are so many different models of the Model M board that some folks never see this happen.

If you can easily lay your hands on a PS/2 to USB converter you might try that. Sometimes that will work 'cause the converter is more tolerant of the power draw and the motherboard simply sees a USB keyboard - so everybody's happy.

fanpeople:
Have you tried it with a different computer?

Did you plug the keyboard in whilst the computer was turned off? If not, restart.

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