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HP 9810/9820 Card Reader Drive Wheel Repair
Posted by Katie Wasserman on 6 Apr 2001, 4:29 p.m.
Like the card reader drive wheel on the 65/67/97/41, the drive wheels on the 9810 and 9820 card readers deteriorate and turn to goo over time. I've found a fast and easy replacement for them -- here's how:
1) After opening the machine (see http://www.hpmuseum.org/disasm.htm) remove the card reader circuit board. Use the red lever at the back of the card to start with then carefully lift it straight up. The card reader is connected to the power supply housing with a keyhole type binding post attachment so you need to wiggle it a little to free it completely.
2) Remove the edge connector (with the wire harness going to the card reader assembly) on the front of the card.
3) Remove the small daughter circuit board from the card reader circuit board going to the read/write head (it just pulls straight off) and set the card aside.
4) Remove the 4 screws at the base of the card reader assembly. The assembly should now be completely free with two wire harnesses hanging off it.
5) Put the assembly on your work surface with the drive belt face down.
6) Remove the 2 screws holding the read/write head in place, remove the r/w head and set it aside. This step isn't crucial, but it makes it easier to work on the assembly and keeps the head from any potential damage.
7) Remove the remaining 5 (or possibly 6) screws on that same side of the assembly the head was attached to.
8) You can now pull the assembly apart, but before doing so, you should take note of where the various parts go, in case you pull out more parts than you need to.
9) Slowly pull the assembly apart, as you do you'll notice (depending on how yours is wired up) that some of the photo sensors and/or light sources are wired together and this will keep you from being able to get the assembly opened up completely. The sensors and sources can be easily removed by just pulling them out of place. They are not glued, screwed or other wise attached, so you can carefully pull them out. With luck, you'll only need to pull out one or two of them. You can desolder them if you need to, but you should not have to.
10) You only need to disassemble the reader to the point of being able to get to the end of the shaft with the drive wheels on it.
11) Now, clean the goo off the drive wheels really well. You'll probably need to scrape it off with a razor blade or sharp flat screwdriver blade.
12) Next take three 5/8" ID x 7/8" OD x 1/8" thick O-rings.
13) Put one around each drive wheel and one in between the wheels. This third o-ring serves to keep the other two properly spaced and sits low enough that it won't touch the card as it passes through. The o-rings fit very tightly and you'll need a needle nose pliers to pull them on without them twisting. You should find that the rings are so tight that there is no need to glue them down.
14) Make sure that all three O-rings touch each other all the way around. They should look a little like the Michelin Man!
15) You're done. Just reverse all of the above steps to reassemble the reader and re-install it in the calculator.
While you're at it, you might want to replace the drive belt on the other side of the assembly. Use another 0-ring for this, size: 2-1/2" ID x 2-3/4" OD x 1/8" thick.
The o-rings are available from Small Parts Inc. (www.smallparts.com):
5/8" x 7/8" x 1/8" part #: U-ORB-208 10 for $1.05
2-1/2" x 2-3/4" x 1/8" part #: U-ORB-230 10 for $4.80
Edited: 2 May 2014, 11:43 a.m.
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