HP-25C bad keyboard -- repairable?

[teenix]

(11-07-2018 04:39 PM)mpark Wrote:  My HP-25C died many years ago but I've kept it around. I have a vague recollection of it developing a bad key and that teenaged me took it apart and the darn thing never worked again.

Anyway, I recently found this forum and discovered the possibility of breathing new life into my old calculator, so I dug it out and opened it up to see what condition it was in, particularly the keyboard.

Turns out it's worse than I remembered. I found a half dozen keys that make intermittent or no contact when pressed.

Is the keyboard repairable? If so, what's the process?

Depends what is wrong.

Broken keys, broken spring contacts, dirty contacts, corroded and possibly broken PCB tracks from battery leakage (blue stuff on tracks) or faulty chips.

Corrosion is fairly easy to spot, and a careful cleaning is a good place to start.

The chips are sensitive to static electricity, so care needs to be taken with circuit board handling to avoid damage.

cheers

Tony