deskthority

I've posted at another site (guess which) but I thought I'd check here too!
I have an IBM model M 1394950 keyboard with a bad 1398012 controller board. Lock lights may blink once when keyboard plugged in but then nothing - no response at all from key presses. I swapped out the controller for a different one with the same membrane connectors (16 + 12 pin) and the board works fine.
The problem is the 1398012 has an SDL plug with a nice detachable cable while the replacement controller has an attached cable - not as nice! I can try replacing the electrolytic capacitors if the symptoms sound typical for bad caps, but otherwise, any ideas where I could find a replacement 1398012 controller or what IBM keyboard years/models use the 1398012 so I could keep an eye out for a donor keyboard? I'd really like to have my SDL cable back!

The 1398012 can come connected to a 1386085, which can be the assembly in a 1390131 keyboard.

The 1398012 can come connected to a 1386085, which can be the assembly in a 1390131 keyboard.

Thanks for the tip. I was also told that Unicomp may still carry a compatible replacement controller and I'm checking with them too.

How are you connecting the keyboard to the computer? I'm wondering if the issue is PS/2 power draw or some other converter compatibility issue. PS/2 is a nightmare with modern PCs, and it's always worth trying some other connection arrangement first. Getting the blinking lights (keyboard controller has initialised) followed by a non-responsive keyboard often indicates the need to try another converter. Model M keyboards seem to be one of the types that are more likely to have this trouble.

Daniel Beardsmore wrote: ↑I'm wondering if the issue is PS/2 power draw or some other converter compatibility issue.

Thanks for the response! I tend to doubt it's the converter since it's a blue cube that works well with my other ps2 model m's, but it's still possible it could be the problem and I'll try some others.

i have a somewhat related question, i hope you dont mind. can you just swap controllers on a terminal board to convert it?

bell peppers wrote: ↑...can you just swap controllers on a terminal board to convert it?

It seems to work - at least I didn't have any trouble putting a 1398012 controller into a 101 terminal board (1394204) - the terminal board board membrane doesn't have the LED traces - just had plug in the right side membrane connector correctly leaving the LED portion of the controller socket empty.

Quick update - I went ahead and replaced the two 47µF 10V electrolytic caps on the non-functioning controller and now it's working fine. I guess not too surprising on one of these old boards.