|Re: HP41C-card reader spare parts (HP 82104A, SN 2014A00430)|
Message #6 Posted by Tony Duell on 9 July 2001, 5:16 p.m.,
in response to message #2 by Mike Tjebben
I've just looked at that article, and there are a couple of things that I do differently when I rebuild HP41 card reader rollers. I am not saying that one of right and the other wrong, just a different way of doing things.
Firstly, when I take off the cover, I undo the _top_ 2 tiny screws on the front, not the bottom 2. I don't think this mattersm though. Then, I always take off the PCB on top of the reader mechanism and unclip the 2 spring contacts under it. Handle these with _great_ care.
Instead of unplugging the head wires from the electronics, what I generally do is hold down the bottom PCB with a screwdriver and unplug the vertical PCB at the back from it (carefully pull it upwards). This PCB contains the 1826-0322 sense amplifier chip, and is the one that the head is wired to.
Take the reader mechanism apart upside down, or small parts _will_ fall out.
When reassembling, I put the roller back in and fit the top part of the mechanism with the pinch roller and the 2 card detection toggles. Then I put the mechanism back into the case and plug in the vertical PCB.
Then refit the 2 spring contacts and the top PCB. Then you can do the first test.
Assuming everything is OK, I put the latches in place _without_ their springs, and put the top cover on. Loosly fit the screw underneath. Hook the leaf springs onto the latches (making sure the insulating sleeve is on the spring in front of the contacts to the PCB on top of the mechanism). Then fit the front panel with the top cover lifted up at the front edge. Push the cover down, and tighten the screw on the bottom. Finally
fit the 2 tiny screws.
One thing, when you plug in the vertical PCB, be sure to align the pads on the board with the contacts on the lower PCB (each contact should be roughly in the middle of the pad. Misalignment (or short-circuits) here could be unpleasant.
As I said, the differences are in the detail. Most of them probably don't matter...