HP-65 card reader problems

[teenix]

The motor voltage should appear on pins 1 and 3 of the sense chip. (3 being GND).

It is possible that the wiring to the sense board and charge pin terminals has been damaged where the insulation ends. Sometimes excessive movement can break most of the wires in the cables at this point and restrict current flow.

Check the connections to the sense resistor (4K64) near the top of the chip.

With the motor free running can it still run with a bit of friction applied, ie still produces torque?

Check that pin #11 on the sense chip goes to almost 0 volts when a card is inserted.

If all voltages and motor seem ok, then maybe the sense chip has failed. Do any parts feel warm to the touch?

cheers

Tony