HP97 memory fault?

[Paul Berger (Canada)]

That does sound like it is potentially a memory issue, and unfortunately the memory is in custom RAM/ROM chips so the only source is likely another 97. One thing I would check is to make sure all of the voltages in the calculator are correct. There is a service manual for the 97 on the MoHPC memory stick that include schematics. The card reader problem may or may not be related. The cards are indeed read into program memory, however since you say your program loops runs for a few minutes before crashing, if it was a memory fault I would expect you would be able to read a card when the calculator is first turned on. Aside from the drive wheel there are a number of other things that can cause cards to not read such as, wrong speed, wheel too high or too low as adjusted by the eccentric, broken or incorrect connections to read head, switch timing, bad connection between card reader and the main board, or a fault in the card reader chip. Incorrect voltages to the chips can also cause card reader issues.

Paul.