|Tech help repairing an HP-41 card reader|
Message #1 Posted by Dave Mabry on 30 Jan 2003, 5:51 p.m.
I would like to see if there is anyone here who might have experience repairing the 41's card reader and can give me a suggestion for repairing mine. Naturally it was only intermittent when I started and now it is totally failed.
I had intended only to repair a bad roller and clean the head. It was intermittently reading properly, it wrote cards correctly most of the time, and the roller was just starting to turn gummy. Since this was my first attempt at really working on this type of reader, I ended up disassembling, working on, and reassembling several times. After trying the tubing fix, then the o-ring fix, then back to the tubing fix, the mechanical aspects of the reader seem fine. It can push the cards through just fine. However, when putting a known good card through for reading, it almost immediately displays "CARD ERR". Sometimes it displays "MALFUNCTION". It never reads correctly. And if I attempt to record onto a card and read the card on another good reader the card is corrupt.
I have interchanged the module with the head and motor assembly from a good reader and it works fine. Therefore I assume the problem is in that part of the reader. There isn't much in that assembly. The motor, a noise suppression capacitor, and the head.
What is likely to be the problem? I haven't tried to change the cap yet, but I'm thinking that might be my next step. The motor seems to turn about the right speed. It is smooth and the card pulls through apparently ok.
Any help from experienced repair folks is much appreciated.