Hp-67 Card reader

[Tim]

I have done a repair on the card reader. The calculator pulls the card through the calculator now. However it keep telling me error.
Any suggestions?

[Randy]

Reading or writing failures?

[Dan W]

More or less what I do, in this order:

Make sure you have a known good card. Helps to have a working 67.

Double check all 5 of the wires from the r/w head. These can come loose easily and it's easy to miss.

Also check all the other wires attached to the PCB.

Be sure the PCB is correctly connected to the mainboard.

If that fails, open it up and check that all 4 tiny balls and the roller are in place, and also the two metal leaf springs are in place.

Try writing instead of reading to isolate the problem.

-- Dan

[Tim]

It fails on reading only.

[David Smith]

A card reader that writes but does not read is almost always a bad tantalum filter capacitor (usually a small blue dipped tantalum) on the card read power line.

[Tony Duell]

Do you have another 67, 97 or 41 (that is, something that can read a 67 card)? If so, try writing a card on the faulty machine and see if you can read it on the good one.

If you can't, check the head wiring, and check the head windings for continuity. There are 2 windings, IIRC, one has red and yellow wires, the other blue and orange wires (but I would have to check that in the schematics). If one winding is open, you can neither read nor write a card, and you're looking for a new head assembly (yes, I have had them fail).

The other thing to check are the decoupling capacitors on the various power lines. If one is defective, you get noise in the read amplifier from the motor. This will stop the machine from reading (although it will normally write OK).

[Tim]

What is the value of the tantalum?
Does anyone have the schematic?

[Randy]

It's the only 6.8uf on the reader board.

Schematics of the 67 and others are
available from http://www.hpcc.org/cdroms/ and are well worth the $. Thank you Tony...