HP-67 - 1612A03018 - Card Reader Advice Requested (was HP-67 - strange behavior)

[teenix]

(11-02-2019 07:27 PM)AndiGer Wrote:  Did you find out what causes the "slippery" and the connected acceleration at the end of the card?
I had that as well several times but couldn't explain why ...
Maybe it is the card itself due to speed is data controlled?

In my cases some cards - often even only one side while the other side is ok - went thru smooth but with motor speed-up at the end quoted by an error message.

Thank you everyone
Andi

The speed control is determined by battery voltage. If it was due to data bit spacing, the cards would go through the reader at different speeds which doesn't occur.

The motor speeding up briefly at the end of a faulty read is due to the way the HP67 microcode works.

The code evaluates the checksum before testing if the card has completed its travel through the reader. If a read error is detected, the program memory gets cleared also before testing if the card is out.

By this time the card has passed through the drive wheel which reduces the load on the motor. This effect must be outside the limits of the speed control and the motor speeds up. Shortly after, the code then tests if the card is out and because it is, turns off the motor.

cheers

Tony