This was originally posted some time ago on Deskthority. Hosting it here for posterity's sake.

Recently I stumbled on a 1393464 Model M off eBay for a decent price. This was a model with custom keycaps made for the American Airlines reservation system. Otherwise it's a normal 2nd generation Model M from 1990. I just think the differently printed keycaps look neat.

It arrived and I found that some of the keys were non-functional and I tracked it back to a dead line in the membrane. Since I'd never fully deconstructed a Model M before I decided to give it a go. Usually I just do the screw mod when the rivets break. Ordered the $10 membrane from Unicomp and it arrived Saturday. Just tonight I go the board all the way back together and it works! Typing this post on it right now. Below are some photos are comments on the process. It was more challenging than I thought it would be, getting the springs and flappers to stay in place while you re-attach the membrane and back plate is kind of tricky ...

Model information, this particular unit was built on Feb 06 1990

Beige/cream barrel plate, this is a new one to me. I've only ever seen black ones ...

Just a quick note on the new membranes from Unicomp: if you have an older M you're resotoring you'll need to trim off the rightmost four lines from the smaller ribbon cable. These membranes work with the older Ms but have the built-in lines for the LEDs on the new models. I just used a razor blade and some patience.

New membrane pre-install...

Keycaps back in and ready to be tested!

All back together and ready to go. All in all not too bad of an experience and I found some threads on here helpful. Just thought I'd share the journey. Not sure how rare or special this particular Model M as it just showed up in my running eBay search. Found some info on the Clicky Keyboards site but that's about it. I think the membrane went bad due to some liquid exposure as it looks like there was some dried liquid in between the sheets. Anyway, should be good for another 28 years now I reckon.