HP-71B MultiMod ROM Emulator - Issues ?

[Dave Frederickson]

(03-29-2021 03:14 AM)Sylvain Cote Wrote:  Maybe the pins are little bit smaller on that machine and it is having difficulties creating a contact with the module pins, I do not know, more investigation is needed on my part.

Each pin socket has 4 electrical contacts. Portions of a card reader pin are not be wiped by the socket contacts so when a different module is plugged in with different socket orientations it's possible that a pin may not make good electrical contact and when all 4 contacts in a socket don't make contact you have a problem. Repeated insertion and removal of the module will wipe the pins and the contacts will begin to work. Eventually all 4 contacts will make contact with the pin and the connection will function reliably.
Note that if some, but not all of the socket contacts are not working, the resistance may be low enough for continuity, but the pin won't be able to carry the full rated current.

You can directly attack the problem by cleaning the card reader pins with solvent or a mile abrasive, like a pink eraser.

Dave