Model M with a single non-working key

[Clavius]

Hi! I have a model M lying around I got from someone. It's a clean IBM blue badge one and its looks to be in a perfect state. Apart from one thing that is; the left CRTL key does not register. ALL other keys work fine. I've tried to reseated the key, but the action works like all the others, also it looks the same inside. I've removed the pcb and cleaned the contacts.
I don't know the history of the board, so suspecting a possible spill I poured isopropyl alcohol in the barrel, and on the side of the assembly at the position of the key. Nothing worked so far.
Any tips before I have to start slicing off rivets?

[Bjerrk]

When you say that you have removed the PCB and cleaned the contacts, are you referring to the controller and the membrane contacts which attach to it?

(By the way, what's the state of the rivets?)

[Clavius]

Yes, that's what I mean, the little controller board that is pressed against the membrane contacts. The rivets are in perfect state, not one missing. This is also the reason I hope to try other fixes because its a bit of a shame to boltmod the entire thing because of one not working key.

[Clavius]

I bit the bullet and removed the rivets to have a look. It turns out one of the lines towards the key has been interrupted by some sort of 'rot', a small 1mm blister in the line. Should be easy to correct with conductive ink I think. Time to order a bunch of bolts I guess

[Muirium]

Aye! You weren’t going to fix that without busting the whole thing open, so feel right about doing the deed at least.

[fohat]

a small 1mm blister in the line.

I avoid alcohol around plastic, it is more harsh than most of us realize.

[idollar]

I bit the bullet and removed the rivets to have a look. It turns out one of the lines towards the key has been interrupted by some sort of 'rot', a small 1mm blister in the line. Should be easy to correct with conductive ink I think. Time to order a bunch of bolts I guess

Agreed. Based on my experience, I will force a boltmod.

[Clavius]

Short update! I repaired the open part with a electronic ink pen and boltmodded the board. It's working perfectly now!
Some observations:
- Screwing in the bolts in the barrel assembly is really hard in between the barrels, next time I'll use a larger drill to create a centering hole.
- Keeping the flippers in their right place while stacking the layers took me a few tries. If I would have fixed the barrel plate in something it would have cost me less time.