Hp-41C card reader - dead

[Vintage63]

I've bent the forks away from the PCB and now when I insert the card, from the right, the motor runs and the wormgear makes the bit it is attached to turn.
Unfortunately the card is not pulled inside it is kind of rejected and pushed back.
I've launched the VER command to do this test and obviously it displays MALFUNCTION on the LCD.

Is the rotation direction of the wheel with the two o-rings, clockwise, correct when I look at it from above? In theory it should be.

Thank you
Marco

[Vintage63]

SOLVED!!! The motor pulls the card all the way but it always reports a MALFUNCTION on whichever card I feed into it, be it with VER or RDTA.
What could be causing this? I have cleaned the head with an ear bud dipped into alcohol, I've used the red card to clean the head as well. I've used empty cards as well ad data containing ones. I'll write a program and see if it saves it as a last resort

[BillBee]

My understanding is that the cam has to be rotated until the tension on the card is just right. IIRC there is a little bit of an offset. I've used a jewelers screwdriver on the slot of the drive shaft - 1/8" turn - test.

This is off my memory of reading one of the repair posts here (or archived).

Hopefully I remembered it right, correct me if I am wrong please.

Bill

[Vintage63]

I did a 360 rotation of the cam and after every turn inserted a card to see if VER or RDTA returned anything other than MALFUNCTION
It didn't work just the same. Other ideas? ?
Marco

[teenix]

(05-24-2022 10:43 PM)Vintage63 Wrote:  I did a 360 rotation of the cam and after every turn inserted a card to see if VER or RDTA returned anything other than MALFUNCTION
It didn't work just the same. Other ideas? ?
Marco

There are some details on this on page 34 of my Classic Notes pdf.


cheers

Tony

[Vintage63]

Hi Tony, I have read the pdf a couple of times. I have turned the drive pin 360 degrees, a bit at the time, to see if it was a card dragging pressure issue and nothing changed. The drive roller on the drive pin spun freely without any sort of friction before attaching the motor.
I'll try taking it all apart again and see what I have missed ?
Thank you
Marco

[BillBee]

Tony is the man.

I have only did the tubing repair and rehabbed a botched repair by someone else who gave up. Malfunction and Card_Error were remedied by the cam adjustment.

You are sure the little white plastic idler is in there too? The wee bugger will fall out and its tough to notice.

From what I have read "o" rings have to be a specific size, same for the tubing.

Other than that I defer to the masters here.
Bill

[teenix]

(05-25-2022 05:48 AM)Vintage63 Wrote:  Hi Tony, I have read the pdf a couple of times. I have turned the drive pin 360 degrees, a bit at the time, to see if it was a card dragging pressure issue and nothing changed. The drive roller on the drive pin spun freely without any sort of friction before attaching the motor.
I'll try taking it all apart again and see what I have missed ?
Thank you
Marco

That is exactly what it is supposed to do when the motor is "not" connected. Turning the adjuster will have no noticeable effect in this case.

However if you insert a card manually you should feel a slight change in drag between the card and the drive wheel as the adjuster is rotated. If not, the new drive (o-rings or tubing) diameter is too small. Set the position of the little dot on the end of the adjuster pin as per the diagram on page 34. This is the position for least pressure between the drive wheel and the card. You can rotate it either way (left or right) up to 180 degrees to increase the drag. After 180 degrees, the drag will start to decrease again.

I would leave it at the minimum drag position and try that out when reading a card. If the drive slips a bit, readjust the pin about 10 degrees and try again (etc).

There is a procedure from HP which measures motor current to set the drag, but old drive couplers may break apart using this procedure because they have become brittle and powdery with age.

cheers

Tony

[Vintage63]

@tony, I have disassembled again the reader. The outer o-ring came off so I super glued it again. Having removed the motor and waited for the glue to set I have reassembled the roller and rolling pin and no motor. The notch on the pin positioned as per page 34. inserted card and it was going in a bit hard so I turned the pin a bit left and right until I could not sense much friction. Tomorrow I will fit the motor and plug the magnetic head cables in their holes and give it another go.
Marco

[Vintage63]

reassembled everything and still does MALFUNCTION every time.
I'm throwing in the towel, for now. I'll give it another go in the future, if at all.
Thank you
Marco

[teenix]

It may not be the card reader mechanics, it could be something else like the CPU board, or the card reader circuitry. That will difficult to narrow down, but an oscilloscope may help to check the operating the signals.

cheers

Tony

[Vintage63]

well I do not have an oscilloscope. nor would know what to do with it, unfortunately
out of curiosity I don't have to close the casing of the reader when I test it, right? there isn't some hidden contact the requires the casing to be closed, is there?

[BillBee]

It will run with the cover off.

-Bill

[Vintage63]

great, thank you Bill. so this is not the issue.

[BillBee]

I feel for you. The readers can be frustrating and walking away from it for a while is not a bad option, if only for sanity's sake.

Its a pain but trying the 1/8" turns of the notch is worth a shot when you feel like looking at it again. There is that right sweet spot. At the least to get a different error message.

Take Care,
Bill

[AndiGer]

(05-26-2022 05:42 PM)BillBee Wrote:  There is that right sweet spot. At the least to get a different error message.

My experience: sometimes individual cards work while pre-recorded from the HP67/97 standard pac don‘t or vice versa.
Very frustrating situation ...
Andi

[BillBee]

(05-26-2022 06:52 PM)AndiGer Wrote:  

(05-26-2022 05:42 PM)BillBee Wrote:  There is that right sweet spot. At the least to get a different error message.

My experience: sometimes individual cards work while pre-recorded from the HP67/97 standard pac don‘t or vice versa.
Very frustrating situation ...
Andi

Yes! Sometimes one can have a "write" but then the "read" fails. I have felt like I was wearing the screws out.

-Bill

[Vintage63]

the o-rings are the right ones, the coupler was made by Teenix. I have aligned the coupler and given it a go before attaching the motor to the frame. How did I do this? Well, I powered the motor and checked that the worm gear was turning without wobbling while the motor was turning. I will now, euphemism, try turning the pin slightly and insert a card, then repeat this operation until the pin has done a 360 degree turn.

Is there anybody in Europe that has the tools to veriify if the card reader does work or not? I could send it to somebody in Europe or send it to the USA - Australia - Mexico but it might be cheaper to buy a used one from ebay, I think.

Very 'frustrated' Marco

[teenix]

Maybe a long shot, but the motor speed may be out of acceptable limits for successful reading or writing.

The card runs through the reader at about 6cm per second so it should take about 1 second to pass through the reader. The speed can be adjusted with a small trimmer located on the CPU board underneath the plastic housing that feeds into the 41.

It would be a bit hard to time the card, but you could mark the adjusters current position as a restoring reference and try fiddling with it.

cheers

Tony

[Vintage63]

Hi Tony, I'll time it to see how long it takes to 'scan' the card. I'll also try to locate the trimmer :-)