HP-65 more on the card reader

[teenix]

Hi Alberto,

If the CPU reads the card then the sense amp and heads must be working. It is unlikely that the actual write circuitry in all the controllers you tried are not working.

This seems to point to a mechanical problem. Dirty contacts, bent contacts, something shorted, something open. The motor inhibit, motor on/off and head on/off switches must be ok or it wouldn't read. That just leaves the write inhibit switch circuit.

The leaf switches look a bit tarnished in the picture are the contacts ok?

The HP-97 has switch contact adjustment screws. Does the '65? If so there will probably be test points to measure each switch between ground. The HP-97 service manual says turn the screws CW until the switch just shorts, then 1/4 turn CCW.

HP recommended not to fiddle with the leaf switches too much because if they bend they may not be able to straightened properly causing tension problems. Cleaning a contact was done with an ink eraser.

Have you been able to see any activity on the WA and WB pins with your oscilloscope when trying to write?

Does the calculator go into program mode with the WPGM/RUN switch?

Can you see the WE pin change when this switch position is changed? (Unless the WE logic only activates during a write)

cheers

Tony