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

[teenix]

(10-08-2022 09:39 PM)albertofenini Wrote:  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 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 ?

Also, I have noted that 6,8 microF is a difficult value to find,
Can it be replaced with something different ?

10, 16 or 25V Tantalum should suffice.

If you look at Tony Duels circuit for the 67, the colors are marked.

http://www.hpcc.org/cdroms/schematics5.0...c/hp67.pdf

The 6.8uF is fairly common, and is available from the worldwide distributors like Mouser, and I see them listed in local hobby suppliers and on the Bay of All. If it is not feasible to get one, try a 10uF.

cheers

Tony