HP-25 resurrection adventure – Part 1: The Keyboard

[Dreato]

Sounds like the keys rows are not getting scanned properly. Open the unit and clean the connection pins and corresponding holes carefully with 400 grit sandpaper. Did corrosion get into the keyboard? If so, you can try spraying a bit of contact cleaner into the holes beneath each key, and pressing the keys repeatedly. If necessary, you 'can' disassemble and clean the keyboard. You must drill out the heat stakes, clean the contacts, then carefully reassemble and reglue. If the calc still fails, I'd try Bernhard's ACT-E. It worked great for me.

Regards,

Dave