HP 65 Card reader task

[jftman]

Here is what I found.

I applied 5.3-5.5v with my supply.
With power on, in run mode grd-p17 is shy, it hovers around what the power supply shows after switching the calc. on. About 4.20 volts.

The two pins 16 and 18 w/respect to ground are that same 4.20 ish volts.
When I put the card into position to trip the motor leaf, I INDEED see p17 drop to 5mv, so that is what should happen if I am doing this right.

P1 sits with 0.00 volts, both with card in and no card. Bad……….
BUT I do not see a ground continuity on p11, it is open to infinity!

I test for ground on the rail, where the black wires go into the plug and card reader motor, with p7 on the sense chip, GOOD.

BUT, using either p7 or my rail, to p11 , reading open on each reference!
This is the same wether or not the card is in position for MTR and if I push it in to close the other two leaf contacts.

Maybe this is why the voltage on p17 is not greater than the pins 18 and 16 with no card in place?
Do I need to look for a lifted ground, or a broken ground to p11 on the sense chip?
This is pretty interesting, what do you suggest?