HP41 Card Reader not Pulling Card



#2

Hi All,
I recently purchased an HP41CV and a card reader.
The CV had some problems with posts and upper screw slots but I think I've gotten that repaired so that now all 4 slots work with modules without the display going crazy.

The card reader had the gummy wheel problem. I followed documented procedures and replaced with o-rings. When I tried it out the first time, it pulled the card thru ok but gave "malfunction". Then I took it apart to check everything and re-assembled. This time it wouldn't pull the card at all- not even an attempt. I've taken it apart again to check, but couldn't find anything wrong.

The motor works if I just connect it to a battery. The CAT 2 shows the correct card reader programs available. If I look under the top circuit board when I insert a card, it looks like the metal strip is making contact ok.

Any advice for what I should check next or what could be wrong?

Thanks,
Colin


#3

Hi.

There are two things I'd like to know: does the motor engage when you insert the card or not? When you tested the motor alone with a 1,5Vcc battery, did it pull the card?

If the card is not actually 'grabbed' by the pulling gear and it is spinning - as is the motor -, then you might want to check if the gear shaft is well adjusted. The 82104A has an adjustable shaft, as you can see there is a cut on it so, with the aid of a screw driver, you can adjust the pressure of the pulling gear. Should insert a card while it is disconnected from the HP41 and gently insert and remove it - in and out the card reader slot - so you feel how the pulling gear is grabbing it.

Success!

Luiz (Brazil)

Edited: 28 July 2012, 3:50 p.m.


#4

Luis,

Thanks for the response.

When I insert a card, the motor does not run at all. When I connect the motor to battery, it will pull a card through, slowly.


#5

Make sure there isn't any "gummy wheel" residue remaining along the card path. Also check to be sure the "clutch" isn't slipping. Some of us have had better luck with soft tubing than with the O-rings too. Here's a previous discussion that might be helpful:

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/forum.cgi?read=227492#227492

#6

Hi.

Quote:
When I insert a card, the motor does not run at all. When I connect the motor to battery, it will pull a card through, slowly.
As I understand, these are new symptoms, observed after you disassembled and reassembled the unit, right? Chances are that you may have a bad connection due to any residues in the contact pads OR one of the wires from the motor is loose. Have you already tried to rotate the gear shaft so to adjust the pressure? It can be done while the card is being pulled when you connect the battery to the motor. It is possible that the shaft is not well adjusted so there is too much pressure while pulling the card, hence more current drawn and - possibly - the motor driver is cutting it. Would the O-rings you used be thicker than needed?

Success!

Luiz (Brazil)


#7

I have cleaned the contacts on the top PC board. I also checked with an ohmmeter between pins 4 and 5 and there is continuity when I slide in a card. I've also re-inserted the red and black wires into the holes several times.

I have not tried to adjust the pressure because I thought that the motor would at least try to start. Are you saying that if there is too much pressure that the motor would not even start? I don't hear any click or detect any movement of the motor.

Oh, and I got the o-rings from hp*classic on ebay. Are those the right size?

Edited: 29 July 2012, 9:16 a.m.


#8

Hi.

Quote:
I thought that the motor would at least try to start. Are you saying that if there is too much pressure that the motor would not even start? I don't hear any click or detect any movement of the motor.
Could you try just one (last?) experiment? After this one I'll be clueless.

Please, remove the shaft and the pulling gear then, with the card reader connected to the calculator (it may be OFF), insert the card and check if the motor starts. This way there will be no mechanical stress/load over the motor and it should spin freely. If it does not happen, then it would be necessary to inspect the circuit whit schematic diagram (I do not have any, sorry). I'd try finding voltage interruptions in the switch path with a reliable, safe electronic voltmeter (as for a definition, all of them are, though).

Let us know how it goes.

Success!

Luiz (Brazil)


#9

It could also be the sensor switches, which are implemented as thin strips of metal and some really tiny pieces of plastic. If the metal strips are bent out of shape, or the plastic piece(s) is (are) missing, the reader will not be able to sense that there is a card there that it should pull at.

(Note: my memory may be a bit hazy about the detail, but I'm pretty sure that I had to adjust the metal strips after my first attempt at reassembling my card reader.)


#10

Quote:
(Note: my memory may be a bit hazy about the detail, but I'm pretty sure that I had to adjust the metal strips after my first attempt at reassembling my card reader.)

Hopefully your memory is hazy, as any "adjusting" of the metal strips is playing with fire. The only adjustment required is for it to be installed correctly. Bending the strips is a one-way ticket for your reader to end up in the junk box.

#11

Hi, Randy.

I was waiting for some 'guru intervention' here... Thanks!

Quote:
(...) any "adjusting" of the metal strips is playing with fire.
Could not say any better... I once had one of these metal strips accidentally bent when reassembling one card reader and I must confess I was lucky enough it bent over the main 'body line', not in the contacts area. I carefully brought it back to the original alignment and it worked fine, but based on its design I know I was lucky (and I knew that then...).

I'm intrigued with this card reader; any chances the motor driver is failing?

Cheers.

Luiz (Brazil)

Edited: 29 July 2012, 7:49 p.m.

#12

Ok, well, it's working now!

Bad news Is I'm not exactly sure why.

Here's what I did:

I took the drive pin out and tried to insert a card. I noticed the motor was running for a short period of time.

I put the drive pin back in and inserted a card. The motor was now pulling a little, but not much and on the display I got "malfunction" and then "card".

Then I tried rotating the drive pin to different positions. No change.

I then used the ohmmeter to check the Card Insert switch continuity - between pins 4 & 5 of the top PC board. This time I noticed that the switch made continuity when the card first touched the contact but as I pushed the card further, continuity was broken.

I took off the top PC board and cleaned the contacts again. I also swapped the two metal strips around.

This time when I put it back together and tried it, the card was pulled through perfectly. I got a card error since it was a blank card, but then I tried to write a small program, clear it from memory and read it back and it worked!

I re-assembled the case, tried again and it still worked. That's all for tonight. Don't want to push my luck :)

Thanks everyone who responded for your help.

One more question. The two metal strips are supposed to be identical aren't they? Why would swapping them make a difference?


#13

Good news, indeed!

About the metal strips swapping: all I can tell is that by simply changing one for the other and reassembling the unit you readjusted all parts with each other: metal strips spacing/postioning, small plastic actuators, PCB positioning... Because of their size, I'd guess this is the best assembly for the set. Chances are that if you disassemble the card reader again, remove parts, replace them exactly as they are now and reassemble it, you'll find a different behavior.

Your 'let it as it is' is wise!

Cheers!

Luiz (Brazil)

Edited: 29 July 2012, 11:50 p.m.

#14

I agree with Luiz...swapping those two parts and the replacing them made the adjustment your card reader was looking for. If you had known the adjustment needed, you could have solved that one problem too that wa, your way did it "accidentally". BTW I use this method a lot on my computer. Unplug something, plug it back, swap 2 if you can...just messing with often is the fix!

I also HEARTILY agree with Luiz...it is working...leave it alone! Good decision you made.

Congrats on the fix, however it happened!


#15

Hi.

Quote:
...swapping those two parts and the replacing them made the adjustment your card reader was looking for.
What do we know... 8^D Well said!

Cheers!

Luiz (Brazil)

#16

Quote:
Are those the right size?
They should be 0.25 inches (6.35 mm) in diameter when installed on the shaft - parallel with the metal hub below them. Larger and they bind, smaller and they don't pull the card.

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