HP97 Card reader. won't read but will write

[teenix]

(08-10-2022 09:03 PM)Dreato Wrote:  The card reader is rebuilt mechanically (o rings, shaft coupler) and electrically (tantalum caps all around). Card sense switches adjusted. All reads give "ERROR". However, I can write OK and the written cards read fine in other machines. The original machine will not read cards that it has written itself.

Any ideas? Help appreciated!

From a HP microcode point of view, the "Error" will be displayed from an invalid checksum or a timeout (eg.slow or stalled card reader)

Other errors will be hardware related.

Two simple things to try:

if you have another CPU board, swap it and try again.
I think you have an oscilloscope, check the signals coming from the sense IC all the way to the CRC IC. The 97 service manual can help with pins outs.

cheers

Tony