Old (big) mag cards?

[John Garza (3665)]

Andrew,

I've seen and was amazed at your work on the Casio! Seriously, you are the only man to ever make me want to buy a Casio.

I have an HP-9100B in need of mag cards. I have a stock of 9800 series cards that are the same thickness and width - just longer. And they work fine in the 9100 and the extra length gives you more of a 'handle'.

I have tried mag cards from IBM typewriters cut down to size. These are Hollerith-sized (as in punch cards). Evidently they reused the media mechanical design from the punch card days. At any rate, they do not work and I'm not sure why. The first program step always reads back in as a 77 (return), regardless of what code was written. I have tried this with 2 cards I made and I get the same error.

The 9800 cards work flawlessly. And both are 0.2mm thick.
Could there be some difference in the magnetic properties of the media itself?

-J