Do you have to "help" cards through the 97?


Hi all,

Just finished replacing the gummy wheel on the card reader of my 97. Many, many, thanks to those who have posted detailed instructions/advice on how to do this, particularly Mike Davis.

I replaced the gummy wheel with two rubber o-rings bought on e-bay. The cards feed fine now, however, I was getting Error with most feeds until I discovered that if I give the card just a little push as it is feeding through, then it reads the card fine. Again, this is just a gentle guiding of the card as the motor pulls the card. Just wondering if this is normal? Or should you just be able to feed the card in until the wheel grabs it and pulls it through with no extra assistance. Again, I would say I am not really "pushing" the card myself, just a little pressure on the card as it is moving.

Thanks for any thoughts!


What is happening is that the card sensor switch is detecting the card and starting the motor before the card is engaged by the wheel, and you are simply moving the card slightly further so that the wheel can fully grab it and pull it through. On a perfectly adjusted card reader wheel using exactly the right size model aircraft fuel line tubing, this won't be necessary, however, I've found this generally to be the case with O-rings, which only partially grip the the card across its width.



I'd add some extra comments to Michael´s. I have noticed that in one of my cards readers the cards are pulled, say, differently. In the newest, G-version, if I hold the cards with the tip of my fingers while inserting them, I feel the card reader ferociously pulling them out of my fingers. In the earliest, E-version, the cards are pulled somehow softer, and in some cases, if I hold the cards with extra strength in the tip of my fingers, I get reading error. In both readers, if I partially insert the card and then push it by using the side of the finger, instead of holding it with the tips, the pulling wheels find their own way reading them, and error conditions do not happen so often.

I once thought it was a matter of adjusting the pressure of the pulling wheel, but it seems to me now that it is related to the motor control. I have not seen the motor power supply and I do not know if the different readers also have different motor control circuitry, but if the earlier units have a different current handling, chances are that either a current peak detector or a narrower speed tolerance might also trigger an error.

My thoughts, though. And my 2¢, too!


Luiz (Brazil)

Edited: 23 July 2010, 12:55 p.m.


Thanks, both of your comments make sense. It does seem that I only need to add a bit of pressure initially when I put the card in to ensure no Error. I have switched to putting the card in part way, then pushing it forward with the end of my finger, and that seems to work.

Thanks for those insights. I really didn't want to have to go back into "surgery" to fix something if this behavior was not normal.



Hi, Keith;

have you tried to adjust the pressure? There is a way to slightly adjust it. I adjusted both my card readers to a minimum.


Luiz (Brazil)


Hi Luiz,

I don't know how to adjust the "pressure" - is there an article on that or what do you do?



Hi, Keith;

My mentioning of "pressure" without a concise reference 'sounded' dull, sorry...

Unfortunately, you'll have to remove at least the card reader's upper cover, meaning the four small screws and the big one in the rear of the card reader´s case. After that, you can follow both this thread and this other one, mostly from the second follow-up, written by Ed Sowell himself (message header) and ahead. If you have not noticed yet, the pulling gear´s shaft has a cut in the outer edge so you can use a small screw driver to rotate the shaft. It has a slight eccentricity so you can adjust its pressure over the card while reading/writing. The follow ups in the above mentioned thread give some info about how to adjust it. If you need extra advice, let us know, OK?


Luiz (Brazil)

Edited: 23 July 2010, 9:59 p.m.


Thanks for the information. Upon further testing of several cards, it seems that some cards read well, while others do not. Do HP 67/97 cards "go bad" after some time? I know they are magnetic media, and as such probably don't last forever. The manual suggests cleaning cards with alcohol solution. Does this really work?

Thanks for any thoughts.



Hi, Keith;

I have a few cards that no longer read their contents, some written by the HP41´s card reader, others by the HP97.

In fact, I had the contents of some old cards (others), recorded in the 80's, recovered after cleaning them with alcohol. You'll see that the card surface reflects differently when it is dirty (flat with some spots) and when it is clean (regular and glossy, not shiny).

I just get some soft cotton with alcohol (not enough to drip, something more than moistened), then I place the cards over an absorbent, clean, straight surface (some sheets of paper over a table) then I firmly press one of the edges of the card (tip of a finger) and then I pass the cotton over the surface with a bit of pressure, in the same direction as the card is read/written (after that, clean the small surface under the finger tip the same way). I have not done it more than twice in one single cleaning, mostly because I am afraid of removing part of the magnetic material OR any protective layer. Anyway, the cotton usually comes out with dirty material on it. I never lost a card with such cleaning procedure, just have many of them recovered.

BUT if they are stored closer to strong magnetic fields OR exposed to direct sunlight for extended periods of time, chances are that their own magnetic field variations AND related contents will change. In these cases, chances are that overwriting may succeed, but it is not 100% guaranteed. Also, I am not aware of any effects on the card reader's head if the card has residual strong magnetic field after being exposed. This should also be taken into account.


Luiz (Brazil)

Edited: 26 July 2010, 12:12 a.m.


Hi, Keith;

I forgot to mention that I also use a soft tissue to clean any exceeding material immediately after cleaning with alcohol. It also helps drying out any residue left by the alcohol itself.


Luiz (Brazil)

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