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To bolt mod or not? (IBM Model M)

A

allCAPPS

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Hello, everyone. I'm posting to get a second opinion on fixing a Model M which has a few keys that aren't working. Any help would be greatly appreciated.

This photo shows where the malfunctioning keys are in relation to the backplate. Curiously, the rivets appear to be okay near where the malfunctioning keys are. But there are broken rivets where perfectly functional keys are. Go figure.

Model M.jpg

You may notice some oxidation on the right side of the image, and I strongly suspect that might have something to do with the problem. From what I understand, the primary purpose of a bolt mod is the re-squeeze the layers together, but I suspect a full disassembly and bolt mod may be necessary just to get to any corrosion between the layers.

So before I potentially go off on a joy-ride bolt mod, is there anything I'm overlooking? Am I on the right track with a bolt mod? :confused:

Specifically:

  • How successful might a bolt mod be?
  • If I were to do a bolt mod, what should be done once inside (other than a thorough cleaning of the contacts and testing for continuity)?
  • I'm out of Deoxit, but would be worth squirting some in the switch barrels first?
  • Is there anything I'm not thinking of here?

Thanks in advance for the help! :)
 
Yup, the "bolt mod" is to hold the whole shebang together after you've cut off the tops of the mushroomed studs to get the thing apart. I don't much care for drilling a bolt hole all the way through. Some (including myself) use washer-head sheet-metal screws. You simply drill a half-cm or so deep pilot hole in the center of the plastic stud and let the screw cut its own threads. Works very well if your plastic studs are in good shape.

I'd be very concerned about the rust on the bottom plate--makes me wonder how much corrosion got into the works.
 
Good to know re the use of screws over bolts. I did read about about that, and of course everyone has their own opinion. If it's good enough for you though, Chuck, I'm willing to give it a try myself.

I'll get to doing the "screw mod" this weekend or next and post the results. I'm thinking the water entered on the right side and worked its way through the layers before reemerging on the bottom. I guess we'll soon find out.
 
I spilled a drink into a Model M and could get get it properly cleaned out. Which is how I discovered the bolt mod. People call it a 'mod' because somehow it was supposed to enhance the operation of the keyboard. For me it was a matter of restoring operation, not enhancing it.

Anyway, it works. I used the McMaster part numbers specified on the Geekhack Wiki. It was tedious. I think bolts are preferred because you don't have to worry as much about perfect drill hold sizing and you can adjust the bolts if needed.

Remember, it's a capacitive keyboard - the buckling springs are there for feel, not for function. Don't bother squirting de-oxit in the barrels. Separating and cleaning the membranes will have a better effective.

Also, the bolt mod is not idiot proof. I had to spend a bit of time tweaking the bolts near the Enter key; if things are slightly mis-aligned you'll have problems with the keys that sit on two barrels.
 
mbbrutman said:
....Remember, it's a capacitive keyboard....
Click to expand...

Are you sure about that Mike?
Look at THIS LINK to Deskthority Wiki.
The Model M is actually "buckling spring over MEMBRANE".

Cleanliness of the membrane is critical. Look at this quote from the same Wiki.

"The membrane is far more susceptible to contamination than the capacitive PCB. Failing membrane traces are not an uncommon problem with old Model Ms."

Greg
 
Last edited:
Yep .. that's it. You caught me confusing the Model M with the Model F ...
 
As promised: An update on the Model M repair. Success!

I opened it up expecting to find a lot of corrosion. Fortunately it was clean, and the corrosion was limited to the edges of the back plate. As for functionality, a damaged trace was immediately apparent and corresponded exactly to the bad keys. The picture shows how much of the trace was missing after I cleaned off the loose stuff. I repaired it with a circuit writer pen as that's what I had on hand. I don't know how durable it will be long term, but if it gives me any trouble in the future, I found out you can still order new membranes from Unicomp.

Every part got a thorough cleaning. The labels were saved. I sanded down the back plate to the bare steel and primed it.

Right now it's being put through its paces as my daily driver, and everything has worked flawlessly save for the num pad '4' which has to be pressed a bit harder. (I just haven't gotten around to tweaking it yet.)

It'll eventually be rejoined with its original system, a PS/2 Model 30.

TL;DR Another Model M saved
IMG_1455a.jpg IMG_1460a.jpg
 
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