HP-41 Card Reader Disassembly


My card reader has begun making a loud squeaking noise when cards pass through it. It still reads and writes cards OK, but I'm concerned that the noise may indicate damage is ocurring to the mechanism. I've tried to open it up to see what's causing the noise, but although the four screws by the latches have been removed, it still won't come apart. It seems as though something is still holding it in the center at the top end. Is this a snap fitting, or a screw, or what? I don't want to damage the reader by trying to force it open. If it's a screw, I csn't figure out where it is or how to get to it.


It's a screw. Remove the label in the "tunnel" and there it is.

When I took my card reader apart, I found that an earlier owner had snapped is post off. The card reader still seems to hold together ok though.

Dare I say it, there may be cosmetic benefits in gently breaking the post. (No, I didn't say that).

The card reader is a little tricky to get back together. A genetic defect that has left me with three very small hands makes the process somewhat easier for me :-)


Aahhhh, thanks Steve! My first attempt at cracking into one of these things was the 4 obvious screws, and there must be something under the rubber foot, like the calculators, but to no avail. As mine has been having the gooey roller problem like most, I now have completely disassembled the jewel, the gear with the roller is a friction fit via the pin with the end that looks like a regular screwdriver should take it out, but not threaded.A little persuasion with a pair of curved hemostats will remove the pin. Now to resolve the sticky roller on the gear. Lets see, that roller material and diameter looks very familiar.....darn near like a piece of fuel line for a model airplane! They make that stuff in all kinds of thicknesses, I'm going to give it a try and I'll repost the results!BTW, the hemostats were for clamping off the fuel line on my r/c airplane; no comments from the peanut gallery please!


Success is mine! Found a small piece of the pink model airplane fuel tubing, the outside diameter measuring 12 divisions, the inside diameter measuring 4 divisions on an engineers scale, 1 inch = 50. Cleaned all the old gooey stuff off the gear, after dismantling the whole giant machine, and slipped it on there, chamfered the edge ever so slightly as to not bind in the housing, reassembled and hey hey we're running like new. An additional tip, while your'e there, clean the magnetic head with a little alcohol on a cotton swab, like we used to do on a cassette player. In dealing with those microscopic screws, use a small touch of cyanocrylate glue on the tip of the screw driver to keep 'em in place till you find the mark. Hope somebody here can benefit from this, I had a real challenge in doing it!


Dave, Thank you very much for this information. I had just bought a card reader on ebay and yes the pinch roller had turned to jelly. I thought I had wasted my money when I come across you message. Went to my local hobby shop and picked some model airplane fuel line. It was 5/32 ID and 1/4 OD. Followed your directions and it is working great. Thanks again for helping out.

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