HP-65 more on the card reader

[albertofenini]

Hi Folks, this is what we did ...
We modified two different card readers, one is HP65 style AMP 1826-0185 and one is HP67 style AMP 1826-0322.
For both we removed PIN 5 (WB) and we added a wire to the card reader PCB, so that we could capture WB before it reaches the logic board.
WA, RA and RB have been left connected to the logic board as GND and the two power lines.
Both card readers still read and load the card.
We have captured WA and WB.
WA looks normal, while WB looks flat and only change status once or twice.
If we connect "on the fly" WB to the logic via the wire, it gets noisy as when is connected thru the usual golden pin.
We also changed C3 (60 microF capacitor) and the results where very much the same,
except that we had to adjust the eccentric cam to keep the machine reading.

   

When looking an the scope snapshot please keep in mind we compressed the Volt scale as
WB change status only very slowly compared to WA, and it was looking almost flat.