IBM Model M Intermittent keys

[famicomaster2]

Hello, I'm new to this forum. I was recommended by a friend to ask here about a keyboard problem I've been experiencing.

I have a fairly old keyboard. It's an IBM Model M. Black and white logo, detacheable cord.
It's part number "1391401" ID number "4036156" manufacture date October 25, 1989.
"Plt No J1 Model M" is also printed on the back.

Well, to put things short, I paid about $5 for this keyboard at a junk store some 10 years ago and it worked great until a few months ago.
It sat in storage for a little while, but at some point something fell on it on one side. It still worked fine, so I've kept it in service.

Well, I made the mistake of making it the only keyboard for my IBM AT. This was a mistake because recently, some of the keys have been becoming flaky. Specifically, 3, E, D, and C. Something tells me that F2 might not be working either, since it's in line, but I can't test it. Nothing happens when I press these keys. I do not get a "keyboard error" message or anything, and all of the other keys work fine.

Removing the key cap of another key and tapping it with a screwdriver will work. Doing the same to any of these 4 keys will do nothing at all. It doesn't work on my more modern computer either.

I've heard something about plastic rivets, but I do not know how to test this. I have had this keyboard apart, but nothing obvious looks wrong and I've cleaned each of the ribbon cable connections. Still nothing.

I don't know if this is an electrical problem with the keyboard or it's microcontroller, but I don't know if this is a mechanical problem or not either. The keys feel the same as they always have and the same as every other key.

Also, the left shift key has been sticky lately, to the point it causes weird errors on the keyboard when the key is installed on the keyboard. It's very soft and does not click. It will stick on or stick off.

Any way I can repair this at home / for cheap? Should I consider just getting a new keyboard at this point? I don't want to put any money into this if I don't have to, it's really beat up and it might as well be worthless. Missing key caps, it's filthy even after cleaning it, and now the mechanism is failing.

Thoughts?

[famicomaster2]

I disassembled the core of the keyboard to see if maybe it was dirty inside... Didn't see anything obvious, so I plugged the membrane in by itself and... I get nothing. Every other letter will appear except that row. Is it my controller or is it the membrane, do you think?

[fohat.digs]

I have never had a problem like the one that you describe, but if it is a single discreet row, then the problem is certainly the electrical connection between those keys and the controller.

If the keys feel right, that is. If the rivets broke free and that section is "floating" then that could be the problem.

[famicomaster2]

I have never had a problem like the one that you describe, but if it is a single discreet row, then the problem is certainly the electrical connection between those keys and the controller.

If the keys feel right, that is. If the rivets broke free and that section is "floating" then that could be the problem.

I actually disassembled the keyboard down to the individual layers of the membrane and cleaned those off. Membrane out of the mechanism, that row of keys still does not work. They are all connected electrically, but they are also wired to the "F1" key... Which works perfectly fine. The computer I am testing with has RAM problems - You have to press F1 to get it to boot into DOS. I can get it to boot to DOS just fine by pressing F1. I can also get into setup with Control + Alt + Escape.

[yui]

I would expect that a trace got oxidized or broke on the row that is non functioning between pads.
I bought a 122 keys that had coffee spilled on it and  half of a row worked but not the other haft and that was the issue, using a bit of conductive copper tape to make a path around the break fixed it (does not need to be exactly on it, on mine i could easily put it between 2 keys before the break and 3 after and all the keys work, at least on that line, i have 3 out of 5 that are fried)
I used a multimeter in continuity to test between each pad until it stopped beeping (if F1 works and not the next one in the row i would start here)(the inside side of the membranes are conductive, but the traces are fine so try to not scratch them too much with the probes)
And if it was rivets, now you will have to bolt mod it anyway so that is going to be fixed

[famicomaster2]

I would expect that a trace got oxidized or broke on the row that is non functioning between pads.
I bought a 122 keys that had coffee spilled on it and  half of a row worked but not the other haft and that was the issue, using a bit of conductive copper tape to make a path around the break fixed it (does not need to be exactly on it, on mine i could easily put it between 2 keys before the break and 3 after and all the keys work, at least on that line, i have 3 out of 5 that are fried)
I used a multimeter in continuity to test between each pad until it stopped beeping (if F1 works and not the next one in the row i would start here)(the inside side of the membranes are conductive, but the traces are fine so try to not scratch them too much with the probes)
And if it was rivets, now you will have to bolt mod it anyway so that is going to be fixed

I've determined that I'm just going to throw it out at this point. I've got a model F in storage anyways.

[Henrythewound]

You should at least salvage the caps. I just bought a model M and it’ll be here tomorrow. It’s missing the F1 and F7 caps. I see people selling individual caps on eBay but I haven’t seen those 2 yet. I’ll buy yours if you are willing and they’ll fit.

[pabile]

I've determined that I'm just going to throw it out at this point. I've got a model F in storage anyways.

where are you located? I'd be glad to fix it or buy it from you if you are near by.

You should at least salvage the caps. I just bought a model M and it’ll be here tomorrow. It’s missing the F1 and F7 caps. I see people selling individual caps on eBay but I haven’t seen those 2 yet. I’ll buy yours if you are willing and they’ll fit.

i still have a bunch from M122 so most probably not "Fx" keys but more of "PFx" if i recall correctly

[yui]

earlier models had PF keys but latter ones had F keys, and if you are willing to ship it (or are not too far from france) i would actually buy this broken board from you, i like fixing stuff. And i'd rather liked it fixed that in the trash.

[Stupidface]

I've determined that I'm just going to throw it out at this point.

It could be more trouble than it is worth (you know best), but perhaps you might consider offering up the carcass somewhere for the cost of shipping, even if that "somewhere" is not here?

It is true IBM made millions of these keyboards, but it is also true they won't be making any more.  I understand you might be anxious to bin it, but someone* might be only too glad to relieve you of it, which is why I ask.





*Alas, no, I am not that someone.

[famicomaster2]

where are you located? I'd be glad to fix it or buy it from you if you are near by.

Southern United States, haha

You should at least salvage the caps. I just bought a model M and it’ll be here tomorrow. It’s missing the F1 and F7 caps. I see people selling individual caps on eBay but I haven’t seen those 2 yet. I’ll buy yours if you are willing and they’ll fit.

I was probably going to pull all the keys and the badge before tossing it. I didn't figure anybody would want a model M with no keys, so I was going to throw it away.