Model M Keys Suddenly Stop Working

[smarmar]

I have a '92 Model M silver label which keys, one fateful day, stopped responding. Just 9 keys won't work. I've highlighted them in the image below. They don't seem to share a grid or sector but I could be wrong. I'm sure there are plenty of you GHers whom are way more knowledgeable than I in these matters. And that is why I ask this question of you, today.
Here's a list of the keys in question:
ESC
Caps Lock
Left Alt
G
H
'"
Up Arrow
Numpad 0
Numpad .

[jim121049]

The keys you listed are all in the same row of the key matrix. If you're lucky, you have a dirty connection where the membrane plugs into the socket on the controller board that can be fixed by cleaning. If you're unlucky, you have a break in one of the conductive traces on the the membrane.

[smarmar]

Thanks for the tips! I diagnosed the problem to where the smaller ribbon connects to the pins. I tried carefully rubbing/cleaning the contacts, drawing new connective tissue with pencil lead, and then slicing a few millimeters off the end of the ribbon, all to no avail. I noticed that when the ribbon lays naturally flat the contacts pull away from the pins a little. I stuck a few thin layers of scotch tape to the back of the ribbon which made it a tighter connection but I was still getting intermittent key outages. I hacked a solution by putting a piece of cardboard between the ribbon and bottom tray which pushes the ribbon upright and, consequently, the contacts to the pins. It works but might not be a permanent solution. Down the road I might end up buying a new membrane and gulp perform a bolt mod.

[fohat.digs]

A bolt mod is not really all that bad, just fussy and time-consuming.

I use DeOxit for cleaning stereo gear, if you had something like that it might be worth trying on your contacts.

[smarmar]

I use DeOxit on my stereo gear, as well. Great stuff. I didn't mention it but I used it on the ribbon contacts and pins to no affect.

I've been meaning to do a bolt mod on at least one of my MMs but I've always been afraid to potentially botch the job. I feel the time to make the leap is close at hand.

[ThoughtArtist]

It could make a good dumpster find for some kid