HP-65 more on the card reader

[teenix]

(02-03-2019 11:43 PM)albertofenini Wrote:  I agree, it looks like there is some high frequency noise there, kind of something would interfere ...
but what could possible generate that noise ?

On the other side, we also have a unit S/N 1333A20538 where both WA and WB looks good
but still it doesn't record anything on the card ...

We will keep trying ...

bad ground connection, on pcb, inside chip, on probe
probe not connected properly, scope not setup properly
open circuit from CRC, or inside CRC


If the WA WB signals appear at the sense amp and it reads ok, then I would imagine faulty write circuits in sense amp. The rest of the circuitry is common between read/write, except the outputs to the RW head.

Can you see any activity from the sense amp pins that drive the head?

cheers

Tony