HP-65 and HP-67 card reader how to test the amplifier ?

[albertofenini]

This actually what I did, Keyboard PCB and motor are trustworthy
I have tried all the three CPU boards with this set and a working card reader

Then I have combined each CPU with it's own card reader (head and electronic)
keeping the known working keyboard set

I'll buy some new caps, these should be : 22microF (qty 2) for the head,
3,3 microF for the motor and 6.8 microF for for pins 16 and 18 of the Sense Amplifier, what voltage is suggested ? (Tantalium right ?)

I have updated the photo book with the values measured for each head

HP-67 Card readers updated

I have a question, if I keep the head disconnected from the card reader pcb and I
want to check the signals when a card goes thru, to which cables from the head should I connect the
probe ?

I think that the connectors are providing a connection (the motor runs
which means it gets power thru the connectors) but with micro currents the connectors could cause a loss of intensity
and the sense amplifier could suffer from this

However, I would like to build a sense tester since this is often the responsible of a non working card reader

Thanks for any hint, take care !!!