I've got a Cherry MX 5000 that I've been using since 1996, and it now stopped working after I removed the keycaps for a bit of cleaning .
I initially though that a key must've got stuck, but when I disconnected the whole keyboard from the controller PCB the problem persisted.
Symptom: When I use keyboardchecker.com (I didn't find a specific software for the mac), "home", "end", "page down", "arrow up" and "0" show as depressed (not released).
Again, this is with only the controller PCB with no keys connected at all. (When the keys are connected, it will behave in the same way, and the modifier keys seem to still work - all other keys don't).
I also replaced my PS/2-USB dongle as I though this may be the culprit - no change.
Has anyone an idea how I may go about to fix this? The controller board does not seem overly complicated, but I have no schematics or any information about it.
I tried my luck in replacing the larger capcitors. When I pulled C1, the board doesn't act up, but when I replace it (even with a new one) the problem resumes.
The IC on the board is a Motorola ZC86963P. I found no information on that one other than that it appears out of production and could probably be obtained from a "speciality" dealer.
I fear that if I go to a "normal" repair shop, they won't probably get very far.
So I'd be really grateful if anybody has
- Any general how-tos in debugging such a problem
- Any schematics or repair information on that board
- Any information on that particular Motorola Chip
- Any information if there is any chance of getting a replacement board