IBM 1395300 Model M2 PCB repair
Same housemate. Same thrift store. Different keyboard. Different problem.
The Model M2 is a much slimmer buckling spring keyboard than the regular Model M, but they grow unreliable with age. The common problem is bad capacitors on the controller PCB. The symptom: Always-illuminated Caps and Scroll Lock indicators, and a keyboard that doesn’t work.
The hard part is actually getting inside this thing. It’s held by screws and plastic snaps. I hate plastic snaps. Loathe them. Once inside, there are two easily-visible capacitors on the board. The small one is 2.2uF 50v, and the big one is 47uF 16v. We weren’t sure which of the two were bad, but based on their track record it seemed appropriate to replace both with new caps from DigiKey.
After removing the capacitors, one of the pads refused to hold solder. I had to run a wire around the back side of the keyboard to a connected point.
Actually, I lied. The really hard part is putting the keyboard back together. Good luck with that.