Hp-41C card reader - dead

[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