Testing the HP65 or HP67 card reader sense amplifier

[teenix]

(11-17-2021 10:30 PM)albertofenini Wrote:  Tony
We have received today the test clips and this has been a big improvement
Now we can read signals without soldering wires

We’ll do more tests in the next days
Using a working HP67 will try to figure out the baseline for most of the signals

However, if we want to start from scratch and we disconnect the magnetic head from the card reader pcb
when a card is read where can we check if the head is working ?
What we should see and where ?
The black cable from the head is ground connected
Then you have colored ones
Should we put the scope probe between the black and each of the colored or between the colored taken two by two ? Red/yellow and orange/blu ?

Thank you very much !!!!

Yes, they are pretty handy for this type of thing.

The Classic Notes PDF has waveforms and connections shown. However the waveforms will be slightly different depending on what is on the card. (If reading cards is how you are testing)

I think the head coils are 47ohm 14mH each as per the wire colors you mention.

You can test each read signal by connecting the scope probe to the CA[6] or CB[10] pin on the sense chip.

The sense chip is a bipolar circuit but it would still be wise to treat it as though it can be destroyed by static electricity.

cheers

Tony