Preemptive strike on 41 card reader


Hello All,
I have a 41 card reader that was purchased "new" at the EduCalc selldown. From my experience with my 67 (and reading the experiences of others) I'm assuming that the rubber wheel will, at some point, do the gummy thing. Does it make sense (i.e. easier?) to replace it while it is still a solid object, or wait until it becomes semi-soft?? Thanks!



Do it while it's solid!
If it starts to get soft, there's a good chance it'll start to "drag" the gooey mess into other parts of the reader and make it more challenging and time-consuming to clean up.

This is from experience that I and my father have had with some gummy versus still mostly solid wheels. The more solid ones clean up so much more easily and you don't get cards gooey too, if you do it early.

Good luck!



I couldn't agree more. I have two card readers and I ensure that if I had changed both rubber wheels before they got gooey, I would have found less difficulty cleaning up internals.

Just a piece of advice, if I may: take care assembling back the front panel, specially the left-sided flat spring. It must be the one with the isolating tape!

Make a good job!


Oh! And don't forget to use a demagnetized screwdriver to save you the trouble of having to demagnetize the reader head! Seriously!

If you forget, you might end up with CARD ERR (I think that's what I remember), even though you've reassembled everything properly.


Thanks for the advice! I've gotten the instructions on the repair and will (carefully!) proceed. Cheers!


Just so that you can read a dissenting opinion here as well :-)

I wouldn't replace a wheel until I have to. Usually, you can detect signs of trouble long before the wheel liquifies to the extent that it contaminates other parts (this is not like the case of those HP-67s that stayed in closets for years until someone tried to use them again, with the wheel completely disintegrated already.) And in any case, I didn't find it the least bit difficult to remove that contamination. So why mess with something that may have years of useful life left in it?



I have noticed that the reader wheels in the 82104A are usually glued to the roller so that they are quite difficult to remove. It takes a lot of scraping and tweezing to get off all the old roller. Once the wheel turns to goo all you usually have to do it wipe the remains off with 91% isopropyl alcohol. This might be a good reason to wait until problems start showing up (O.K., I'm lazy).

I have a reader that I bought about five years ago. It has the original wheel in it and it get used regularly. I have been waiting for it to start messing up, but so far it hasn't. I'm keeping it intact just to see how long it takes before it dies.


My experience is that if you wait until the roller has turned to glue, it's easy to remove the remains from the gear assembly (just wipe it off), but
you also have to clean up many other parts of the reader. If you do it before it's turned to glue, then
the reast of the reader won't need much cleaning, but it's a lot harder to clean off the remains of the old roller. I just did an HP67 where the roller was just starting to decay and I had to
spend quite a bit of time scraping the roller off the gear shaft.
It's up to you. If i get an HP card reader in for repair for some other problem I normally replace the roller anyway (unless it's obviously new or still OK). If it's my own machine, I replace the roller when it needs it.

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