Card reader repair in a HP-67

[jbssm]

Hi all,

first of all, I must say this is a very technical problem and perhaps really difficult to solve ... still I'll try cause this seems the best form to try and find an answer.

I'm trying to repair the card reader of a HP-67 calculator.

This is what I already did:

1 - Cleaned all the gummy well remains

2 - Replaced the gummy well by 2 O-rings

3 - Revised the shaft mechanism

4 - Since after the above is was still not working, I also calibrated the screws in the golden metal plates so that they are on with a card inserted and off without a card

Still, although the card passes, I always get an error.

The only strange thing I notice is that almost at the end of the card passing, I hear the motor still running for more about 0.1 sec. before it actually stops ... I don't know if this is normal or not since I think it also happens in working units when you put a bad card in and gives error on reading.

Now, is there someone that can help me solve this problem?

Edited: 23 Nov 2006, 1:46 p.m.

[Klaus]

If you suppose that the mechanical part works, you should replace the capacitors. I replace the capacitors on the card reader PCB and the capacitor that stabilizes Vbat. I use electrolytic-caps as replacement.
The article-section on this website contains some more information, and I can send you a photo of my HP-67 with the capacitors, polarity and values marked.

Good luck! Klaus

Edited: 24 Nov 2006, 2:05 a.m.

[jbssm]

Hello Klaus,

yes, if you could post the pictures that would be a great help.
I've read about putting new capacitors, but I really never figured out exactly what I had to replace. so if you could send a picture of them replaced that would help a lot.

Thanks.

Edited: 25 Nov 2006, 8:09 a.m. after one or more responses were posted

[Klaus]

I don't know how to post pictures. Send me an email throught the museum's mechanism.

[David Smith]

If you have accesses to another machine, try and write a card on yours and read it on another machine. A machine that writes but does not read is usually caused by a bad tantalum capacitor on the power line at the reader chip. It is usually a small blue dipped tantalum electrolytic capacitor.