HP97 Card Reader: recording problems (rephrased)


Hi all HP97 users and fans;

I had a somehow interesting experience with my HP97 yesterday night. After reading and writing a few magnetic cards, it started to show [ Error ] in the display when trying to write (read was fine). I disassembled the calculator and tried to readjust the sensors without success. Then, for the first time in this unit, I removed the card reader´s PCB and took a look at the contact plate.

It was slightly bent and I decided to remove it (five small screws). I cleaned it and decided to plain it. After a few small torque on the opposite direction, the contacts plate was almost plain again. I reassembled it and readjusted the contacts. Now it is working fine, again, but I noticed two small different behaviors in the card reader operation.

Although I've done all procedures the best of what I think, the card reader now seems to pull the cards a bit slowly, as if it is a bit more difficult to pull them in. Should that be due to excessive pressure in the contacts plate? Also, in one of the read/write operations, I touched the card prior to pull it out of the reader and it seems to me that it was slightly pushed back in backwards. The card reader motor started to run again and it stopped only after removing the card from the inside of it. An [ Error ] message was shown, again. Has anyone of you, guys, experienced such behavior?

I'm affraid of having to open the calculator again in order to readjust the plates. What I did was to slightly tighten the screws till each contact was close, by measuring the three connection points (M, F and H), and then slowly loose them back till the contact was open. Then I gently inserted and removed one card and checked if each contact was closed and opened. All seemed fine and after that, the card reader started to record again.

Any suggestions? Should I left it this way? If there is excessive pressure when the card is pulled inside the reader, both motor and magnetic head may be working outside their specifications. Is there any way to check for that?

BTW, I have some pictures of the reader PCB, component and solder sides. Should I post them here?

Best regards.

Luiz (Brazil)

Edited: 29 July 2005, 11:44 p.m.


Hi Luiz,

I am not sure if the contacts are the rootcause. Couls it be that the pressure of the rubber capstan is a bit higher than before, did you tried to give the black axis a little turn. I hope my explanation makes sense, otherwise I can send a .jpg of what i mean.




HI, Ronald; thank you for your followup.

You see, I thought about adjusting the roller axis, but since I did not touch it, I thought it would be a good idea to leav it as it was. If the adjustment you mention is the same, or close to, as the adjustment of the HP41 card reader (82104A), then I know what you mean: the excentric axis.

Based on the fact that I actually tried to leave the contacts plate as plain as possible, I thought that, after readjusting the screws, the small plastic actuators, that cause the contact blades to touch the pcb when the card is pulled in, might be pressing the card surface a bit more than before. Also, the pcb screws themselves. They were somehow thighten when I removed them, so I tried to screw them back as tight as I thougth they were.

Thank you for your valid suggestion. You see, I try not to disassemble the HP97 too much because it has too many moving parts and connections, and I have to take care of them all when either openning or closing it back. I`ll do that tomorrow again. In addition to the axis, any other suggestion?

Best regards.

Luiz (Brazil)

Edited: 30 July 2005, 11:41 p.m.


Hi Louis,

Yes I did mention the exectric axis. I have no other suggestion, assuming that the contacts are as clean en smooth as they were before.

There is one thing that comes to my mind now, there are 2 (if I recall th # correctly) small "guidance" springs in the side of the cardreader path(about 1 cm long and bend).
I assume they are still in place, smooth surface and can move freely ?



Hi all.

Pardon me for commenting; I don't own a 97 or a 41C card reader.
So I am sticking my nose in possibly where it is not wanted.

From many years experience repairing a very wide range of equipment,
for copiers to mining machines and computers, I know of the damage one can do if one modifies the machinery too much.

It sounds like the capstan pressure is indded a little higher that normal and the motor is EXCESSIVELY loaded. I suggest you carefully re-do the job to correct this, as you may get failure in the electronics
(if any) which switches the motor. The ERROR message you are getting is IMHO, a timing error due to the slower card scanning speed, which I guess would now be at the margins of operability.

If you keep running the 97 in this state, don't be surprised if
something fails. Just trying to help...

Kind regards from Down Under!

Don Wallace


Hi, all;

first of all, thanks to all of you that either added valid suggestions to this subject or at least wish to help somehow and were not able to. Also, thanks to all of those who have already placed posts in the past about the HP67/97b reader; because I read many of those I agregated many new knowledge to my own about these masterpieces.

With no further ado, I opened the HP97 again and checked the excentric adjustment. After carefuly inserting a card, I tried to reduce the pressure by adjusting it and I noticed that it was almost in the lowest pressure adjustment. Based on the difficulty on inserting the card, I assumed that this unit has a new rubber puller, an O-ring perhaps (I did not open the card reader mechanics). So, by setting the lowest pressurew possible, I adjusted the contact blades again and now the cards smoothly 'walk' through the card reader´s head, either reading or writing. Even the noise from the motor + pulling gear has been reduced somehow.

About the contacts adjustment, I once read an adjustment procedure that worked for me. I'm not sure who posted it, so I'll not even try to wrongly refer to someone, so forgive me the one who posted it! The HP67/97 card reader has three contacts: one that senses a card has been inserted, another that senses the card 'position' so it can be read/written, and a third one that senses if the card is protected or not (read-olny card, cannot write on it). This adjustment procedure states something like to make sure the three contacts are closed wihtout a card inside the reader, then one should slowly recess (unscrew) each screw while measuring the related contact(ohmmeter) till it is opened. By finding the closer screw position where the contact is opened, recess it 1/4 of a turn (90 degrees). After doing that with the three contacts (and related screws), gently insert a card and check if the contacts close with it inside the reader. Remove it and confirm that they are opened. I'd also add that the small plastic actuators, the ones that actually push the contact blades when the card is inserted, should not offer too much resistence to the card insertion, and if that happens, maybe you should have a look at the contacts plate and check if it is not bent or twisted.

BTW, to those that have gone any further with these readers, I still have two questions: the 'normal', average current measured when motor is pulling a card and if there is any way to adjust the motor speed.

Wow! I wrote too much. Hope this helps as a partial guidance to those experiencing related problems with card readers. If anything I wrote here is not in accordance with either regular procedures or specific card reader adjustments, please, I'd thank for any corrections and/or additional info to this post in order to avoid dammage to calculators or related devices.

Best regards and thanks again.

Luiz (Brazil)


The procedure I use for adjusting 97 card reader contacts is essentially the one in the service manual (on the CD-ROM set).

With no card in the reader, connect an ohmmeter across each contact in turn (there are testpoints for this on the reader PCB). Screw in the appropriate adjusting screw until the contact just closes, then back it off 1/8 of a turn (or so). Check that the contact switches reliably when you put a card in (if it doesn't, suspect bent or dirty contacts).


Hi Luiz,

you asked:

"BTW, to those that have gone any further with these readers, I still have two questions: the 'normal', average current measured when motor is pulling a card and if there is any way to adjust the motor speed."

Please see my recent post on HP67 card reader speed adjustment on this list and the responses from various people - there is all the info you need to get your HP97 card reader into perfect condition.

BTW, for spare motors, I buy those HP41 card readers advertised as "defunct" on Ebay (cheap because defunct - always was just the rubber !) and put those motors into my HP67s. Alas, some of the motor screws are glued so the screw heads must be milled off.


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