HP-67 Card Reader became very touchy

[teenix]

(09-03-2022 02:14 AM)YoungerThanThat Wrote:  I have replaced the power supply capacitor but it did not fix the problem. I have the feeling that the engine is slipping at the end of reading a card. There are few cards where it stops correctly at the end but most of them seem to be spinning longer than it should and then I get an error.
Anybody wants to buy an HP-67?

This operation is normal. It has to do with the HP microcode, which controls the reader, and when it detects a card read error. If an error is found, it takes a little longer to turn the motor off.

This will most likely be a checksum error where the card data does not match the calculated checksum, which is the last record on the card.

One thing that doesn't get mentioned much is the magnetic head. These are quite old now and can also suffer wear and tear. Some that I have seen are quite badly worn from cards rubbing over the top surface and I guess this reduces the pressure of the head slightly against the card surface and maybe just enough to reduce the signals that are read from the card. The writing may work fine because of higher magnetic signals, or errors could still be introduced. Unfortunately, writing poor quality data to a card does not produce an error.

You could try adjusting the concentric shaft that supports the helical drive gear to increase the pressure slightly (if it isn't at max already)

My Classic Notes has details on adjustments on page 34.

cheers

Tony