HP-65 - card reader with WB wave noisy - FIXED and RESTORED

[teenix]

(05-06-2019 11:10 PM)albertofenini Wrote:  ciao Tony,

with "driverless" we mean a keyboard PCB without Anode and Cathode drivers,
thus "driverless"

The test showed that whether there are or there are not the Anode and Cathode drivers on the keyboard PCB it makes a difference in the WA and WB behavior

We can surely replace the capacitors on the logic board and see what happen,
I also had read that post.

However, do you know how can we check the goodness of the magnetic head ?
At the moment we can not measure the impedance but we could measure the resistance values.
Do you know between which cables it should be done ?

Do you think that connecting a capacitor from the WB pin of the hybrid and the ground would help ?

Thanks for help !

Ahh ok.

Aren't the Phi1 Phi2 system clock signals generated from the anode driver? If that is missing, then I would assume the CPU won't work.

I would assume the
orange/blue pair
then
yellow/red pair

They are just small coils so should have some inductance/resistance to measure from a DC source. The impedance will also depend on a signal frequency through the coils.

A capacitor there might just distort the square wave signals.

The reader chip seems to have a bit of black magic in there

cheers

Tony