Which resistance controls the card reader speed on a HP-97

[Francois Lanciault]

Hi,

I just finished refurbishment of one of my HP-97 card reader but this time I have a problem. I cannot get rid of the ERROR message when reading a card.

I have changed the rubber rollers and cleaned everything. I have check the alignment of the nylon ball switches and verified that they work as intended with a voltmeter. The clutch is working well also.

The card goes thru smoothly but I always get an error message when I try to read cards. Write operation do not produce error messages but I don't think any check is performed on write operation and reading card written this way also produce an error.

So the only thing that looks not normal is the speed of the card going thru the reader. It is faster than what it should be. I have adjusted the eccentric nylon shaft to all possible position but the speed is always too fast.

I had the same problem once with a HP-67 and I added a trimmer to adjust the speed and eventually it work as intended. The information on where to install the trimer was available somewhere on the net... but I cannot find this information for the HP-97.

Sure it can also be some defective chips, but first I would like to get the speed right before giving up.

Anybody knows ??

Thank you.

François