HP-65 more on the card reader

[albertofenini]

Hi Tony,

scope setup is the same for all the other units, and we soldered same cables at the end of the card reader PCB to attach the probes,
hence I would exclude bad connections fo the scope or a bad setup.

We checked all the joints on the original card reader and we built another one stripping
all the components, clearing the PCB and soldering again, from scratch, I would exclude bad joints on both.

The amplifier, unless two different chips have the same problem, which may happen but I think is unlikely, should be out of discussion

We have not measured activity other than at WA, WB, RA and RB pins.
We can check activity at the head cables and on the other Amplifier pins.
However, two complete different card readers giving the exact same waveform ??
It has to be something else ...

We'll check and post.

Anyone has a suggestion for the other serial number ???