HP-41CV won't power card reader?


I have two 41CV's. One is a fullnut and the other a halfnut. The card reader works perfectly in the halfnut, but not the fullnut. In the fullnut, it never "engages" and grabs the card when inserted.

Other than the card reader problem, the fullnut works perfectly... I even tried inserting an Advantage ROM in the #4 slot where the card reader plugs in. The module is recognized and I can do a catalog 2 without error.

Any ideas??



It could be in the fullnut the batteries are potent enough to run the calculator but not enough to drive the motor in the card reader. I have a halfnut CX and fullnut CV and whenever I do any card reading (and especially writing) I make sure the stronger set of batteries I have is in the calculator. One of the two sets is just fine to do about anything I want EXCEPT drive the card reader.

Try swapping your battery sets between calculators first.

Does CAT 2 on the fullnut list the routines in the Card Reader when the reader is installed?



I should have mentioned that I did already try a battery swap. Your cat 2 suggestion was a good one, though. I did that, and the fullnut does indeed see the card reader functions when it's plugged in.



The only thing I can think off is that there is something fishy with Port 4 that renders it adequate to detect the Advantage and Card Reader ROMs but not enough to power the card reader.

I suspect there could be some wear or fraying of the plating on the contacts. I was having weird behaviour in with the card reader in my CV, and on taking the calc apart I noted there was some crimping of the contact along an edge of the male connector for Port 4. I gently flattened the crimping with a thumbnail, gave everything a good clean with 99% isopropanol, and all is fine since.

I don't know if this is your problem specifically, but it seems that the issue is in your fullnut calculator, not in the card reader.



Did you try BRAND NEW (shouting) batteries in the full nut? It sure sounds like a battery problem to me. As I remember it, this is how I discovered that my full nut took more juice than my half nut. The same used batts would run my reader in my half nut, but not in my full nut. New batts in my full nut did the trick.


The problem is most likely corrosion on the battery/port connector strip. Open up the machine and clean all the contacts with 91%+ isopropyl alcohol.

Could also be related to bad screw posts not keeping the circuits clamped together well, or wear on the port contacts.

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