HP-41 card reader producing strange sounds


My (20+ years ) trusty card reader started producing strange rumbling sounds when card is pulled through. It reads the card fine but I have never heard this sound before. It sounds like some screws got loose and something vibrates when the motor is running. My question here is should I go open it and tighten (what?) something. I have never opened one of these things so I would like to hear from some of you that have (way) more practical experience. BTW, I do have all the documents about replacing gummy wheels and PPC CD's with detailed description of opening the CR, but I don't remember reading anything about this strange rumbling sound.


Edited: 24 Apr 2004, 9:19 p.m.


Hi, Miki;

I remember having the same problem, but mine did not write cards correctly, although sometimes it could read.

As you have the documents about replacing the gummy whell, note that there is a worm gear (endless thread) mounted in the motor's axle that rotates the driven (pulling) gear and I had two readers with this wornm gear slipping when the axle rotates. But as I mentioned, the most immediate symptom is that the cards slow down their speed when pulled. When the reader is reading cards it may not be a big problem if the speed does not vary too much (there is a separated "sync" track recorded beside the data track), but when the reader is recording cards, these cards may not be easily read. In fact, even if the sync track is not be uniform, the reading process may be performed by a "normal" card reader, but it may be way too irregular that the reader with problems may loose data when reading them back.

Have a look at the article about the gummy wheel under the heading "All clean?". Read the last paraghaph and you'll have tips on how to fix this with cyanoacrylate glue.

Hope this helps.

Luiz (Brazil)

Edited: 24 Apr 2004, 11:47 p.m.

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