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Author Topic: Model M Keys Suddenly Stop Working  (Read 1366 times)

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Offline smarmar

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Model M Keys Suddenly Stop Working
« on: Thu, 07 February 2019, 17:44:19 »
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 .
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1992 IBM Model M | Tesoro Durandal[Browns] | Hi-Tek Series 725[Space Invaders] | Tandy Enhanced[Sliders] | Dell Quiet Keys | Mitsumi[AT]

Offline jim121049

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Re: Model M Keys Suddenly Stop Working
« Reply #1 on: Thu, 07 February 2019, 22:52:07 »
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.
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Offline smarmar

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Re: Model M Keys Suddenly Stop Working
« Reply #2 on: Sat, 09 February 2019, 13:43:58 »
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. :-\
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1992 IBM Model M | Tesoro Durandal[Browns] | Hi-Tek Series 725[Space Invaders] | Tandy Enhanced[Sliders] | Dell Quiet Keys | Mitsumi[AT]

Offline fohat.digs

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Re: Model M Keys Suddenly Stop Working
« Reply #3 on: Sat, 09 February 2019, 13:48:14 »
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.
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Offline smarmar

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Re: Model M Keys Suddenly Stop Working
« Reply #4 on: Sat, 09 February 2019, 14:38:34 »
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.
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1992 IBM Model M | Tesoro Durandal[Browns] | Hi-Tek Series 725[Space Invaders] | Tandy Enhanced[Sliders] | Dell Quiet Keys | Mitsumi[AT]

Offline ThoughtArtist

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Re: Model M Keys Suddenly Stop Working
« Reply #5 on: Sun, 10 February 2019, 13:41:07 »
It could make a good dumpster find for some kid
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