deskthority

Recently picked up a 5251, she's from December of 1979 and remarkably clean. I converted it to USB and have been using it for work, but occasionally a few of the switches don't activate when I press them. Like, they physically don't flip the pad, I don't hear the click even when fully depressed. After letting go and trying again, they'll work every time until I stop typing for minutes at a time. They don't feel any different from any of the switches that actuate normally every time, has anyone else had a similar experience?

I know the answer is probably take it apart and check those switches but I'm desperately hoping there's something quick I can do without resorting to that. I'm a lazy bastard

Never heard anything like this. Sounds like something might be sticky inside of the switches that prevents the capacative pads from separating from the pcb. I'm afraid you will have to open them. (Maybe it's not necessary to take the individual switches apart, though)

As soon as they work normally, can you "resummon" the issue by spamming the key really hard and fast?

No, actually spamming it repeatedly tends to prevent it. That sticking theory would actually perfectly explain what is going on.

Might just be some gunk crumbles from the insulating foam that got stuck on the pads. I know that happened to me, but I realized it before putting it back together

Bang on the money. Don't feel like swapping out the foam yet, that feels like an all day project, but I cleaned up the PCB of the crumbs and it's a lot better now. Thank you