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I have a big trouble with my card reader (HP 82104A, SN: 2014A00430) in use with a more than 20 years old -but always correct working- HP 41C-calculator (SN: 2007A00307).

The reason for the card reader-trouble is a damaged pressure roller inside of it. Once it has dissolved into a gluey mass/substance, which glues on the magnetic card and stopped this running through the card reader.

Now i'm searching for this roller as a spare part, because the big HP can't make such part available. The production of HP41C an all the accessories like the card reader had been strictly stopped since some time.

I only need the little roller without the gearwheel -that is quite OK. Perhaps also the roller inside of other HP-calculators/card readers such as HP 67 or HP 97 can be an alternative solution, when it is compatible to that one in the HP41C-card reader (what I don't know).

So, who can help me to bring my good old card reader in funktion again and not throw it away as a throwaway society does some times.

Thank you for helping answers.

Dieter Sippel

Dieter -

Try reading the instructions at the link given below. I've used this method on 3 card readers with outstanding results!
The O-ring is easily obtained in the U.S. at Home Depot stores, but I'll bet is also easily found in Europe (I'm assuming that's where you're from).

Good luck!

-Mike

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=57

Actually, I'd like to give credit to my father, John. He repaired two of the card readers I mentioned and I did the third.

He and I did NOT unsolder the connections when we made the repairs - we were careful to move them out of the way.

Also, we made the mistake of using a magnetized screwdriver in our work and had to disassemble everything and reassemble it after discovering that it wouldn't work until we de-magnetized the head.

Again, good luck!
I bet, if you follow the instructions, you'll end up with a better-than-ever card reader!

-Mike

Although the original part is unavailable, you can rebuild the existing roller.
Take the reader apart and remove the roller (it sounds like you've already done this -- if not, I can
talk you through it). Then scrape off the remains of the old roller.
The best thing I've found to replace the roller are silicone rubber O-rings. These are available (at least in the UK) from companies that sell model engineering materials (that's stuff for people who make miniature steam engines, not normal model shops).
The size I use is called '005' and IIRC it's 7/64" inside diameter, 15/64" outside diameter, 1/16" thick. A couple of those pushed over the tube attached to the original gear (this makes sense if you have a card reader in bits)
works fine in every HP41, 65, 67 and 97 reader that I've repaired.
FInally, put the reader back together and test it.

Hi, Mike

thank you for your very fast response to my lonely helpcry. It's not only very fast but also very good. The given link is rich in substance and will actually help me, I think and hope.

You're right with your assumption, that I am from Europe, especially there from germany. And here are O-rings also well known, so my earlier idea was still in this way. Now i'm sure the repair can be a success.

So once more thanks to you (and your father John)

-Dieter

I've had nothing but trouble using the O-rings. All the ones around here seem to be a smidge too big and put too much pressure on the cards (that cant be adjusted out with the cam pin). I was given some that were the right size but what happens is the "rolling pin" works it way between the two o-rings forcing them to drag on the sides of the reader housing.

What I have found works best for me is the silicone rubber fuel line tubing for model airplanes, etc. The trick with it is to make sure that it is truly round and the hole is centered. Easier said than done... I bought eight different types and only one was perfect.

Dieter-
You're most welcome. I'm glad that I was able to point out something useful to you, but cannot take credit for the original article by Dave.

It's guys like him and Tony Duell and David Smith and MANY others who are really the experts and have help ME before!

Viel Gluck! I kann nur ein bischen Deutsch sprechen!
(Hope that's right - no umlauts, however).

-Mike
p.s. Order the CD set from this hpmuseum site! It has a wealth of information and manuals and repair manuals, etc.
And view the old archives - they've got great tips too! I sometimes miss things and have to go back and reread for fear I'll ask something that's already been covered by these pros!

I've used O-rings on many card readers and never had any problems. For example I did my own HP67, and have read several hundred cards with it since, no problems.
Perhaps I've just found a source of good O-rings :-) (FWIW, I get them from GLR Distribution in the UK).
But I've never managed to find a piece of silicone rubber tubing that works. I don't doubt it _can_ work, but I've not managed to find the right size.
Anyway, one thing is that I use O-rings a little smaller than is commonly recomended (I think the latter are 1/8" ID. 1/4" OD). That may explain why mine end up slightly smaller, which would help a bit.
Incidentally, the 1/8" ID O-rings are ideal for replacing those in the HP9100 keyboard. There's supposed to be a rubber O-ring on the metal pin attached to each key in that machine. Most of them have long since decayed and fallen off. Replacing the entire set makes the 9100
keyboard feel a lot better.

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...

The tubing that *does* work is silicone rubber 1/8" ID x 1/4" OD available from Small Parts Inc (www.smallparts.com). Their part number is: U-210005-10 (for 10 feet of it for $24.24). I've done litterally dozens of roller repairs with this and the readers have never failed to work. It's very high-quality stuff with a perfectly centered core. I've recomended this tubing to several other collectors and they've had the same results that I have.

I too have used this tubing and it is best by far. The inner hole is very concentric with the outer diameter.
The tubing that I bought from small parts is just a little loose on the inner shaft so I put a drop of Testors model cement to secure the tube. There may be other adhesives that work too, but I know that super glue does not work well from experience.