HP-67 1706A00901 [RA and RB with Spike, doesn't read - doesn't write]

[albertofenini]

I have swapped the CPU board with a known working one
The spikes on RA and RB have disappeared and the original card reader worked !

I also have uploaded more pictures for this unit, and I must say that the label
on the CRC chip (which I had totally ignored) probably should have inspired me a little

Also for this unit, RA and RB measured at the CRC chip with the card reader disconnected are clean
but when the card reader is connected the spikes show up.

This happens only with this CPU board.

Looks like also in this case the CRC chip is probably the one to look after ....

Updated Album : HP-67 1706A00901

thanks again for the support ! take care !