HP 82104A Card Reader for HP 41 - Repairs


Can someone out there point to a useful article or thread dealing with the repair of HP 41 Card readers. The main problem is the replacement of a perished rubber capstan drives. We have done this as a service to southern African HP users for many years but the success rate of my little workshop is tailing off badly. I realise the 82104As are all getting older and there may be more electronic failure but the rubber material used and diameters of replacement capstan grommets are critical and the specification of the part we were using may have altered etc. Any useful jig designs would help as well because three-handed workman are getting scarcer and fitting parts in position correctly is vital!



although it seems you know the nuts and bolts, this article has been more than helpfull. It is kind of a starting point. About references to the pulling O-rings: I found good replacements in old, conventional carburators used in some Brazilian cars. I was given a pack with many O-rings with different sizes, external and internal measures. Many of them work fine.

The article pointed above is avery good reading. Please, give it a try. You'll not regreat.


Luiz (Brazil)

Edited: 18 Aug 2004, 3:38 a.m.


Looks really cool and many thanks Luiz, also Dave the "lostrabbit" and Ty, who'll get the postcard when the job is done!


Just to second Luiz's recommendation, and also
by Mark Hoskins which gives aquick fix approach (no need for complete disassembly) if the gummy wheel isn't too far gone.

Both articles were of great assistance recently and helped me resurrect a card reader I picked up of e-bay a couple of months ago.

Best wishes



I use o rings 2.57x1.78 mm (it is an standar size). Material is 70NBR100. They work just perfect.

I hope it helps




The O-rings I used are #006 and according to the spec sheet are outside diameter 1/4 inch, inside dia. 1/8 inch and the rubber is 1/16 inch thick - don't know the material as they came in a mixed pack of various sizes from an auto-repair shop.

Fortunately I caught the gummy wheel in time before it had spread goo every where so could use the abbreviated repair procedure.




If you must use o-rings size 005 (just try and find them) are 15/64" OD. These are the proper size to use. Unlike silicone fuel line 1/4 inch o-rings are too hard to squeeze and put too much pressure on the card/motor drive.

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