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hp-67 / hp-97 card reader repair hints (wheel & clutch)

Posted by Bernd Schmeling on 3 Apr 2002, 5:47 p.m.

I do not want to post the complete repair instructions, this is postet and documented a lot of times before. Best article of repair I found on and , in which I really easy and successful followed to repair my both hp's.

In addition to that, I like to share following experiences:

1. I was able to take the measure of the almost desintegrating drive wheel. The outer diameter of the rubber (I took the measurement of a wheel, that was nearly complete) should be 6.15 mm.

2. Clutch problem. After repair of the hp-67 hp-97 the reader worked fine for a couple of attempts. Suddenly it became poor, the mechanism did no more pull the cards smoothly and became more and more stumbling while pulling the cards. Investigations about this brought following result: The clutch between the motor and the spindle is made of a stuff, that is similar to the stuff, which the drive wheel is made of. So it did not desintegrate, like it is known by the wheel, but it is hardening, so the motor bolt is just running through. To solve this problem, I removed the spindle from the motor, pulled of the clutch and used as replacement a well fitting insulation of a wire, I found in my 'trash-box'. Now I had a really good working clutch, that was able, to transport the card smoothly through the mechanism, but if stopped by force, that released the motor to run free through this 'replacement' clutch.

Why making so much afforts to make a working clutch, instead of fixing the spindle just with 'super-glue' directly onto the motor bolt?

Because of two reasons: If there is no clutch, and if the mechanism might be blocked of any reason, what will happen is as follows: The (screw-like) spindle will keep turning to the wheel with all its power. The result will be, that the spindle will destroy the wheel.

Second what 'might' happen is, that the blocked motor could be destroyed by overheating (I don't really beleave in this, because every motor I know is able to withstand a blocking for more as a several seconds. The reader's motor will be shut down by an error message on the display of an hp after a very small time!)...

So, if you like to avoid hazards like this, you must not have a fixed connection between the motor bolt and the (screw-like) spindle!


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