deskthority

Hello,

I just finished cleaning up a Model M, along with replacing six broken rivets with bolts and noticed the S and F keys require a hard press in order to register. All other keys work correctly. I’m 99% sure the keys were working correctly before I cleaned it.

The S and F keys seem to operate and sound correct and the spring and flipper look fine - the spring isn’t bent and the flipper moves easily. I pushed on the flipper with a toothpick to rule out the spring and they both required the same hard press as when the key caps are installed whereas the adjacent keys register with little effort.

I loosened up the bolts in case I had tightened them too much and that had no effect. My next step is to perform a full bolt mod and test the membrane once everything is apart but I wanted to see if there’s anything else I should try before I take it apart. Thanks.

Try to remove the spring, and put it back on. (Or replace it if you have extra springs). There's various methods without doing a full bolt mod, like:
https://www.youtube.com/watch?v=SnBsDeKs54w

What I do is simpler, I just rotate the old spring counterclockwise, and pull to remove it. It's a bit counter-intuitive, but you need to rotate the spring in the direction in which if the end of the spring bites into the plastic, rotating in that direction would make the spring diameter increase, to release friction forces. And to put on the new spring I use a very small philips head screwdriver that fits inside the spring, and I put electrical tape around it, so that if I compress the spring onto the screwdriver I compress it about 50% it's original size. I then gently put the other end of the uncompressed spring so that it touches the nub of plastic that is supposed to hold it, and I push down with the screwdriver, so as to compress the spring. I rotate again counterclockwise to put it on. I have about an 80-90% success rate with this, so occasionally I have to throw away springs, that I don't put on right, and accidentally bend.

that's sounds like the black rubber foil has deformed when you putting the keyboard together and it interferes keystrokes. suggest you to take the keyboard apart to make sure parts are put up correctly.

Thanks I will remove and if needed replace the spring first and if that doesn’t resolve the issue I’ll take everything apart. That’s what I get for trying to get out of doing the full bolt mod...

Thanks again for the advice! I replaced the spring following pandrew’s method but the keys still required a hard press, so I went with anthonymak‘s method and did a full bolt mod.

When taking apart the foam and membranes I noticed some plastic shavings in between the layers of the membranes from drilling the partial bolt mod. I think that caused the issue because now the keys are working correctly after checking everything out and reassembling the layers.

I appreciate your help and should have a fully working keyboard now.