HP-65 - 1605A02841 - Weird display behavior

[albertofenini]

Hi Tony, hi everyone
we made a little progress with the card reader.
We tested the value of the resistor and it was correct, it was 4.66 KOhm vs 4.64KOhm,
so we re-soldered the resistor, we also replaced the capacitor with a new 3.3 microF one.
However nothing didn't change.
Then we replaced the sense amplifier with a spare 1826-0158 and it started to work.
Is reading consistently although we haven't tried to record a card.

Then we measured with a scope Disp0, Disp1, Disp2, Disp3 and Disp4.
We don't know how these should look like, but Disp0 is different from all the others,
while the remaining four are all equal.

Please look at the pictures, what do you think Tony ?

HP65 - 1605A02841 Disp0 thru Disp4 waves

Thanks again for all the suggestion !!