HP-41 Card Reader always runs

[Chris Murphy]

I got a card reader (via e-bay) that had the gummy wheel problem. Using Dave the "lost rabbit"'s excellent instructions on repairing the hp 82104A card reader, I removed the gummy problem and put it all back together. However, when I pluged it back into my HP-41, it started running immediately and did not stop until I pulled it out of the slot. BTW, I had the calculator off at the time of putting it in and taking it out. I placed the reader back in again and tried to turn on my calculator, but nothing happened. Anyone have any thoughts or suggestions?

[Vieira, Luiz C. (Brazil)]

Hi;

just a hint: remember those golden plated contacts along the card path? They are "activated" by the card itself. If, by any means, one of them os missaligned and permanetly ON, the circuit will "sense" a card and try to pull it in, switching the motor to ON, too. In this case, the power supply will be almost directly connected to the motor. This may cause the calculator not to turn ON . Verify if those small plastic actuators are assembled correctly OR the metal lids are inverted or bent.

Success.