HP-65 card reader - purpose of WE pin

[teenix]

(05-03-2019 09:47 PM)albertofenini Wrote:  Guys we fixed it !
We tested the switches and the WPS switch was not closing at all ...
We had to work a little has we raised it too much and then it was always closed
However we got the right position and now it read and write cards like new

From the 97 service manual, the procedure is to turn the screw until the contact just closes, then back the screw off 1/4 turn.

Even though I didn't physically test my previous hypothesis, your repair proved what I mentioned about the WPS being open circuit causes a write error. In your case the CRC would have thought the card was write protected, aborted the write and gave the correct error indication.

It is interesting that the data is still fed to the card reader as it passes through. I also noticed on a 67, that during a read, the WA WB pins have activity as well, but it doesn't exactly match the read data. I haven't checked, but maybe as card data is being shifted in to the holding buffers in the CRC, it is also being shifted out on the WA WB pins but delayed because of the time it takes to initially fill the buffer. As the sense chip is in read mode, the WA WB pins would be ignored.

Well done Alberto

cheers

Tony