HP-41 Card Reader

[n1msr]

I just got a USB re-chargeable LiPo battery for my 41CX from Diego Cruz, and was looking forward to using it to power the HP-41 card reader. However, the wheel was gummy - actually it had largely disintegrated. I looked at 3 or 4 sources online to learn what I needed to do, but after fitting o-rings for the wheel, the card reader doesn' seem to detect a (HP-67) card when inserted. I know that the motor and mechanism is OK because when I apply a low-ish voltage (~3V) to the motor terminals it runs and the magnetic card is pulled through the slot.

So I assume it must be the card detection that is not working. I read that the two narrow contact strips need to be aligned - I think they are but I have no way to tell if they really are other than seeing that they are correctly seated in the narrow channel and make contact with the small plastic pivoting pieces that they meet at one end.

The two copper "bowed" pieces look to be in place. The little plastic roller is also OK and in place (the bit that likes to skydive from the bench to secret places on the floor).

I am looking for a bit of guidance. I hope the above description makes sense.

(I would like to comment in passing that accessing the 41 card reader seems a whole lot easier than accessing the on on the 67!)

Thank you,

Mark

[Hiwi]

Hi Mark,
what does it mean 'does not detect' ?
Do you get a 'malfunction' or 'card error' message?

Have you tried to record a program and read it back?
Do you have a Nov64d module installed? On newer CX there is a minor issue due to the change of the power management. There is a thread about that issue. Try it without any modules installed.

Was the reader fully functional before the roller became gummy?

And the roller axle is excentric, did you adjust it? The correct adjustment: Apply 3 volts to the motor, and measure the current, it should be about 200mA.

In some cases the card is not pulled evenly enough.(Or too fast). May be not enough pressure => adjust axle.

Did you clean the card, that may be done with den. alcohol.


Ralf

[AndiGer]

Mark,

What I understand is the motor doesn't start when you insert a card?
If so: Did you read this thread? Some hints in there.

https://www.hpmuseum.org/forum/thread-21330.html

Andi

[n1msr]

Firstly, thank you to all who replied. The links to 41 card reader threads in this forum helped me understand that I need to check the alignment of things in the card reader. I had seen the HP maintenance manual but was originally put off by the poor quality images. However, in one of the forum threads, someone (Marco?) posted really nice photos, so going back to the HP "official" guide would be possible.

My 41 card reader did work fine for many years after I acquired it in the late 1990s. The forum thread (Ignazio/Diego/others) provide plenty of food for thought and things to try.

One important bit of information I did not include was that before I dis-assembled the card reader to clean the gummy wheel and replace with o-rings, I did get an error (don't remember the message, apologies) on the calculator and I heard the motor seem to try to run very briefly. But it did not pull the card through at all.

Post o-ring repair, the connection of the card reader to the calculator does not seem to be acknowledged by the calculator at all. But the motor itself does work and as mentioned, pulls the card through nicely.

So something(s) seems as if it is not connecting correctly. I do not have any other modules in the calculator. I don't own any HP-41 modules - althought the one mentioned in the HP maintenance manual sounds like it could be worth having!

QUICK UPDATE: I sometimes get a brief (very short) sound of the motor and the message "MALFUNCTION" and then "CARD" in the 41 display.

Thank you.

Mark

[n1msr]

The 41 card reader is working OK now in my 41CX. The issue seemed to be that I had tightened screws too much on the PCB that lies above the tongue card detection mechanism. I removed the screws completely and applied increasing but gentle finger pressure until it worked. Now the screws are back in and the card reader re-assembled. All is good.

One question though - who built, i.e. put together, that cover and latch mechanism on the card reader for production? Was it pixies with magic dust? That was hard!

Mark.

[rprosperi]

(03-09-2024 10:50 AM)n1msr Wrote:  One question though - who built, i.e. put together, that cover and latch mechanism on the card reader for production? Was it pixies with magic dust? That was hard!

You know the graphic they show on large boxes that indicate it takes 2 people to lift? I've always thought that for reassembling the card reader, there should be a caution label that shows it requires 4 hands, it's the only sensible way to hold all the tiny parts in place...