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I have problems with my 41CX cardreader. It has gotten some sticky liquid in it, and it smears the cards badly with an error message.
Can anyone explain how to fix it, or shall I just send it to FixThatCalc for repair?

Cheers, Matti Sweden

This problem is commonly known as "gummy wheel". There's an article on fixing it on the forum:

HP 41 Card reader Repair

If you're not comfortable doing it yourself, you can have it done professionally.


Hello Matti,

More than likely the drive wheel material in your card reader has broken down, and deteriorated into a gummy sludge. This is a common problem in the card readers of all early HP machines and is due to age.

There are two sets of directions (from two different people) that describe the repair procedure here.

Good luck, and best regards, Hal

You will need either the fuel line tubing or the O rings to replace the gummy wheel.

I have repaired two of these in the past month and they work great!!!

You can get the O rings from this gentleman on ebay:

Wheel Rings

Hope this helps.

Edited: 6 Sept 2008, 12:30 a.m.

and Thanks to all respondents!