HP 82104A "CARD ERR" error

[wongkarcanada]

Greeting. I am a newbie to HP calculators and to this forum. Any help is appreciated.

I collect calculators though mostly Casios. I recently acquired an HP 41CX, which comes with a card reader with a bunch of new and used cards. The card reader didn't work at all, of course, since the original roller had long ago turned to goo. So I purchased a "repair kit" consisting of proper sized O-rings. I have repaired the reader so that it is now mechanically pushing the card through. However, any time the cards (previously recorded ones) are pushed through the display shows "CARD ERR". Not knowing if the cards actually were valid I found the "WALL" command as well as the "VER" command. None of the new cards that were written by the "WALL" command could be verified with the "VER" command (or could be read, for that matter). So it looks like the card reader is not able to read cards at all.

So what would be the common reasons that would cause the reader not to read cards? The inside of the card reader appeared to be in good shape with no obvious signs of damage. The R/W head looks OK as well.

Thanks.

[Erik-M]

My personal experience:

- bad batteries, check first with a new set
- too much pressure, the axis of the plastic gear with the roller is concentric, if you turn it and position the little dot on the screwhead opposite the motor the pressure is minimum. some o-rings are a little larger than the original roller.
- slipping o-ring, clean the metal axis very well with IPA and fix the outer o-ring (or both) with a very little superglue
- dirty gears, clean with IPA and use a very little oil suitable for plastic on the gear

other possibilities:

- slipping coupler between motor and wormgear, rebuild or use a little superglue
- dirty recordinghead, the remains of the original roller can be everywhere, clean very well with IPA
- head out of alignment, I have no experience on how to solve this
- worn out bearing of the wormgear, a little bit of molygrease in the hole where the axis rests can solve this. It is reported that the cardreader makes a bad noise if this is the case but I have no personal experience.

I am not an expert on cardreaders but I repaired a few and had some that had card errors after the repair. I could fix all of them.

[wongkarcanada]

Thanks Erik-M will try some of these suggestions.