HP-67 bouncing keys

[Kees Bouw]

Hi all,

Recently I repaired and restored an HP-67. It works very well except that it suffers from bouncing keys. It is quite useable, but the unwanteded repeats happen often enough to be annoying. I cleaned the keyboard in exactly the same way as my other HP-67 which does not have bouncing keys at all. The bouncing one was manufactured 5 years before the not bouncing one judging by the serial number. So I thought, are there any passive components like capacitors or resistors etc. involved in the de-bouncing process or is this done in the software alone? For example, a capacitor could have degraded over time and replacing it could possibly fix it. But if the de-bouncing is purely done in the code then I guess I will have to clean the keyboard again hoping for a better result. I clean it by soaking small strips of aquarelle paper in DeOxit gold and sliding them under the key domes while applying some pressure.

Kees.