HP-67 - 1909S02534 - Card reader advice requested

[albertofenini]

(01-27-2020 11:26 AM)teenix Wrote:  

(01-27-2020 09:47 AM)albertofenini Wrote:  Hello Everyone,
after a bad moment in our lives with the loss of my father,
we re-opened our lab and started to work again on our toys.
Yesterday we restored an HP-67 that was in working condition but showing some wear,
you can see some pictures here :
HP-67 1909S02534 - Full restoration
However, the card reader, although rebuilt, it keeps giving an error message.
This is what RA and RB looks like :


What would you suggest to do ?
Thanks for helping us out !!!

Hi Alberto,

Indeed a sad time. Memories are forever.

....

The only thing I can see is the timing of the signals looks skewed. They should overlap as in the attached read image.

The idea of this approach is to provide a self clocking mechanism for more reliable data transfers.

Why it would be skewed is a mystery, but it might just be oscilloscope timing.

Does it write ok?

cheers

Tony

Thanks Tony,
they look a little dirty too so we were thinking of capacitors to be replaced,
we haven't tried to record and read on another unit, which is a good hint,we'll try it out
and keep posting !

Thanks for your words, Alberto