I have a TRS-80 model III.
It has a keyboard. It doesn't work so well. Some keys don't work, others are flaky.
So I opened it up and popped the keycaps off.
I removed the keyboard assembly. It's an Alps 12KE010C.
Well, that explains some of the keys not working at all. The only thing protecting the keyboard PCB from the plastic post in the base of the computer is... nothing. Oh Radio Shack. Were you already beginning the long slow slide into oblivion?
Still doesn't explain flaky keys. So I desoldered a key, since that's the only way to get them out.
I measured the resistance when pressing the key.
160kohms?! That's just wrong! Let's open this thing up. It's easy: you just pry on these tabs with your fingernails and they just pop apart.
The inside of the bottom contains the contacts.
Those little dimples are supposed to press into the rubber conductive material inside the dome. And press they did. I suspect these keys weren't meant to stand up to much use. 640k keypresses ought to be enough for anyone.
Lacking true contact cleaner, I just scratched up the contacts and dimples with a screwdriver to maybe get rid of oxidation. I also rotated the dome 90 degrees so the dimples can press into fresh rubber. I put the key together and...
87 ohms! That's more like it.
63 more keys to go :(