HP-41CX Port 1 and 3 temporarily malfunction

[rprosperi]

(11-23-2020 08:13 PM)JurgenRo Wrote:  The other day I plugged in the Games-Module into port 1 of my HP-41CX. The machine did not recognize the module (CAT 2). Same result for port 3 (CAT 2). Plugging the module in port 2, CAT 2 resulted in a weird display (flickering of some special characters, BAT annunciator on) followed by a blank display with a locked up machine finally.

Removing and immediately reinstalling the batteries cured the malfunction: CAT 2 showed the Module in any port. Fortunately no "memory lost" occured either.
What could have been the reason for this misconduct?

If other modules work fine in all 4 ports, then the Games module you are using is defective, or perhaps the contacts need to be cleaned.

It is rare, but 41 modules do go bad - I suspect there are multiple failure modes, and of course how they have been treated for 40+ years is also a factor.

The simplest way to clean the contacts is to fold some fine (500+) sandpaper and run it gently over the inner contact surfaces of the fingers (which will touch the board inside) of the module interface. You could even try cleaning the contacts with alcohol on a Q-tip before resorting to sand paper.

Don't press/rub so hard w/Q-tip or sandpaper that you bend the shape or position of the contact fingers! If you look into the interface, you can see the fingers are nearly touching, only apart enough to grasp the contacts on the board inside the 41 I/O sockets.