Some keys of my IBM Model M are mistyping (not logic board)

[Modano]

Hi everyone,
I'm puzzled about this one.
I've 4 Model Ms, including 2 "1391402" AZERTY layout, UK made, 1995.

Recently, I brought to work my 1391402, as after a little survey, it seemed nobody will care that much about the extra noise.
This keyboard was used by my brother about 10 years ago, and honestly, in my mind it was working but I cannot guarantee that (this can have an importance).

What I did at work was to clean it up with compressed air, and with antistatic foam, wait 1 minute, and thoroughly clean it with air.
Then I remember that my original USB to PS2 adapter was not working, so I tried another one.
The strange part is here. I remember using it a couple of minutes, and somehow I noticed that typing "d" would type "cd". Then I tried other keys, and it was pretty messy : "xs" instead of "s". The first row and last row of letters seemed unaffected.
THen I read some resources, and was pretty sure it was a power issue. Tried with 3 USB hubs, USB2 & 3, all on differents ports, with or without rebooting. Nothing could be made (same on my colleague laptop).
Then I decided to bring it back home. Before putting it in my cupboard, I said to myself that I could try it once before putting it aside.
And, to my huge surprise, there was the exact problem on an PS/2 KVM, and , even on an original IBM PS/2 itself.

The symptoms are : The mid letter row (q,s,d in AZERTY) are always double typing : s -> xs, d -> cd, and other weird stuff. Return adds a * after the Carriage return, Num Lock press types 1 , but some keys are unaffected (keypad etc....)
I thought it was the foam which blowed the logic board (even though it seemed unlikely).

So I put the keyboard fabric (with 2 membrames I redraw using a pencil pen) on the other keyboard case, using another logic board -> same problem.
So it seems the problem resides in the keyboard. I tried to cleanup the membranes, the groundigs. Tried injecting Contact cleaner under the key cap of affected keys...Nothing. Still the exact same behaviour.

Is there a way to clean (using ungreaser for instance ?) the circuit board below the keys ? May it be something else ?
How would you clean the membrane contacts ?
What do you suggest ?

Thanks

[arakula]

What I did at work was to clean it up with compressed air, and with antistatic foam, wait 1 minute, and thoroughly clean it with air.

I got no idea what your "antistatic foam" might be, since to me that's the stuff you stick ICs into so that their legs don't get bent on a journey, but I presume that's some cleaning foam you sprayed onto the board, right?
As said, I don't know what you used, but "antistatic" normally means that it does conduct, at least with a relatively high resistance. If so, it's a bad idea to use something like that on electronic equipment.

The symptoms are : The mid letter row (q,s,d in AZERTY) are always double typing : s -> xs, d -> cd, and other weird stuff. Return adds a * after the Carriage return, Num Lock press types 1 , but some keys are unaffected (keypad etc....)
I thought it was the foam which blowed the logic board (even though it seemed unlikely).

Doesn't seem unlikely to me, based on the above, but I rather think that it seeped into the left or right side of the keyboard assembly (left, presumably, based on the symptoms), between the membranes, and now shortens two or three matrix lines there.

So it seems the problem resides in the keyboard. I tried to cleanup the membranes, the groundigs. Tried injecting Contact cleaner under the key cap of affected keys...Nothing. Still the exact same behaviour.

I guess you mean that you cleaned the visible part of membranes.

Is there a way to clean (using ungreaser for instance ?) the circuit board below the keys ? May it be something else ?
How would you clean the membrane contacts ?
What do you suggest ?

If it is as I assume, your only chance will be to do a bolt mod, since you need to remove a short on a part of the membrane that's between the plastic and the metal plate.

Oh, and don't you ever "inject Contact cleaner under the key cap of affected keys" again. That's utterly useless, since there's a rubber sheet between the hammer below the spring and the membranes below it, and also can have the neat side effect that the hammer gets stuck.

[Modano]

Hi, and thanks for your feedback.
about the foam, I can give you more details, but yes, it is a cleaning foam, but it got in contact a very short time.
I tracked back some chat logs I had at this point with a colleague when I put the keyboard in place and it was working for a couple of minutes without any problem until it began to degrade.
So I finally went to the nuts and bolt (in progress) but at least I removed the plastic rivets and there was this rusty traces and corroded circuits in two of the foils (and evidence that a massive leak of liquid on the mat happened)
Without silver pen, I carefully cleaned with cloth and 3in1 contact cleaner the intermediate foil which was pretty dirty, and individually did some of the tracks.
An early test (all removed, pressing on the foils themselves) showed that it works now.

And yes, your advice makes sense once you see how it is made

[Modano]

Hi all,
I've done a classical bolt and nuts update.
Thanks to all the posts, pictures so on, my keyboard is alive again.

I have some concerns, though :

-1 key (n) is sometimes double typing. LEt's say it happens every 5 or 6 key presses.
- The feel is a little less clicky. For my understanding, this is may be due to the fact I ruined 5 or 6 half moons while drilling. For info, I drilled and put nuts+bolts on all the rivets. May be this is due to the fact that the plate is not tight firmly enough (I need a 2mm key to finalize the tightening) ?
- My N key is not centered between its two neighbors. Also, some keycaps are a little bit lower. I noticed I have 3 white keys, and all the other keys were grey. Any idea ? Are there different keys over there ?

Thanks

[Snowdog993]

I noticed I have 3 white keys, and all the other keys were grey. Any idea ? Are there different keys over there ?
Thanks

I can answer the 3 white stems question easily.  They are for the F, J and number 5 on the numpad.  Those keys are the only ones that have nibs on them to align your hands to the keyboard when you type.
IBM did that with quite a few keyboards.

[Modano]

Thanks
Put them in previous positions

[fohat.digs]

- The feel is a little less clicky. For my understanding, this is may be due to the fact I ruined 5 or 6 half moons while drilling. For info, I drilled and put nuts+bolts on all the rivets. May be this is due to the fact that the plate is not tight firmly enough (I need a 2mm key to finalize the tightening) ?

-  Also, some keycaps are a little bit lower.

Minor mistakes and damage should not be a terrible problem if most of the work was accurate.

With nuts & bolts, you have the opportunity to tighten and loosen them individually to "tune" the feel.

I use M2 size hardware, and so a 4mm socket held in my fingers (no handle) twisted down "finger tight" is about right for me. Others use the full tool and torque the nuts down hard.

Remember, you now have dozens of steel fasteners replacing what were merely melted blobs of plastic before.

With the 1-piece barrel frame of a Model M, if the keys are not even, it must mean that they are seated differently.

[Snowdog993]

- The feel is a little less clicky. For my understanding, this is may be due to the fact I ruined 5 or 6 half moons while drilling. For info, I drilled and put nuts+bolts on all the rivets. May be this is due to the fact that the plate is not tight firmly enough (I need a 2mm key to finalize the tightening) ?

-  Also, some keycaps are a little bit lower.

Minor mistakes and damage should not be a terrible problem if most of the work was accurate.

With nuts & bolts, you have the opportunity to tighten and loosen them individually to "tune" the feel.

I use M2 size hardware, and so a 4mm socket held in my fingers (no handle) twisted down "finger tight" is about right for me. Others use the full tool and torque the nuts down hard.

Remember, you now have dozens of steel fasteners replacing what were merely melted blobs of plastic before.

With the 1-piece barrel frame of a Model M, if the keys are not even, it must mean that they are seated differently.

What Fohat said.  You should have all the bolts tensioned across the board equally.  This can be done, but it takes time and patience.  Don't crack the barrel frame.  If you torque too hard, that can happen.

[Modano]

Hi all,
I've tighten (or at least tried to evenly tighten) a little bit more all the bolts.
The clicky feeling is better

My double stricking of the n key happens much less, but happens nonetheless. This is the very only key that has such a problem.

I suspect either dust or plastic garbage went inside the funnel ?...
I must find the time to remove everything , but maybe this can be the consequence of something else ?

Thanks

[Snowdog993]

Hi all,
I've tighten (or at least tried to evenly tighten) a little bit more all the bolts.
The clicky feeling is better

My double stricking of the n key happens much less, but happens nonetheless. This is the very only key that has such a problem.

I suspect either dust or plastic garbage went inside the funnel ?...
I must find the time to remove everything , but maybe this can be the consequence of something else ?

Thanks

You may have the hammer under the N key out of position, and may have to reseat the key.  Make sure the hammer isn't sitting cockeyed in the hole and the spring can move freely in the barrel, and not be "stuck".  You could use a toothpick or paper clip to seat it if it's not straight.
Make sure the key stem is properly on the spring too.  Make sure the click works.  If it still does this, you may have a problem with the contact sheet, or a short between the contact sheet and the backplate.  That's my guess.  I can't think of anything else.  (Perhaps checking the contacts between the controller and the membrane..)
I hope this helps.

[Modano]

Hi,
so no hammer problem, reseating the key, changing the key does not help.
The only point is that this key is totally offset (lower, and too far on the right) regarding the other keys, so I suspect the buckling action is a little bit altered and may hit twice.

Here is a couple of pics



By the way, it became much worse, nearly 2 out of 3 strokes are doubling. Note that the click sound is totally normal and pars with the others.
I'll remove the bolts and check if there is no garbage ok a vintage of a plastic part that may bend the plastic keyboard at this point .

[Modano]

Hi,
after a bolt removal process, I cleaned up the contact foils, where some plastics debris remained.
I only put about one third of the bolts, instead of putting them all, and didnt overtighten.

Currently, no geometry problems, nor contact keys problem... wait & see