HP-97 Card Reader - Only works sometimes


Hi all again,

I've cleaned the card reader of my HP-97 from the gummy well and replaced it by O-rings.

Now the card passes ok, but most of the times it says "Error" only about 1 in every 5 times it reads correctly.

How can I solve this?
Does this have anything to do with those screws that are holding the golden metal plate inside, how should I proceed?

Best regards and thank you all for this fantastic forum,



I just received an HP97 today with the card reader defective.
So I hope the problem is only the capstan. I will try to repair it very soon, so if I experience problems like you have got, I will let you aware.

I have changed in the past the clock inductance on an HP67 just to speed up the machine about 20%, the card reader was not affected with already written cards.

As far as I remember the aspect of the magnetic surface was very important, I mean it should not be glossy or with finger prints.
Let me time to analyse the things.



Hi, jbssm;

Does this have anything to do with those screws that are holding the golden metal plate inside, how should I proceed?
Most certainly. Also, you should check if the heads are cleaned. It would bve a better idea to check the heads, firts. If not, go to the adjustments.

When I got the HP97 I have now, it had the following sympton: everytime it was turned on, the card reaedr started working and the message Error was shown in the display. After that, all of the calculator functions worked except the ones related to the card reader. It could not read from neither write to cards.

All I did was to adjust the screws. Each of the three screw adjust a thin (and very sensitive) metal blade that act as a contact. Each blade is moved by a tiny plastic wheel Their functions are as follows:
detect when a card is inserted (and turn the pulling motor on)
detect it is in position to be read/written and
detect if the card is either protected or 'written-free'.

Without any card inserted in the card-reader, all of these contacts must be in open position, then they might close, each one at a time, when a card is inserted. Tony Duel once post that the suggested adjustment is to turn each screw in at a time till the very moment that the corresponding contact is closed, then turn it back 1/8 of a turn and check if the contact is open. As we have three contacts, there are three screws.

In the same printed board (I have some pictures at home, if needed I post them later) you can see four soldering contacts alined with each other, each one with a different leter closed to it. These are the 'testing points' for the contacts, being the fourth point the common one. You can use an electronic ohmmetter and verify each contact status through these contact points.

Hope this helps for now. If needed, let me know and later I'll post some pictures showing these 'elementes'...


Luiz (Brazil)

Edited: 24 Mar 2006, 12:26 p.m.


Most likely you need to clean the head. The best way to clean the head is to disassemble the reader. Or you can use the red cleaning card. If you dont have the cleaning card you can wet a card with 91%+ isopropyl alcohol and feed it through the reader several times (it will probably slip and need to be pulled through manually). Then wait for the alcohol to dry.

Another problem could be a failing tantalum filter capacitor on the power lines to the card reader chip. It is a dipped tantalum cap that is usually blue in color that fails.

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