HP9100A back to


I just got an old HP9100A that was in a dump together with other rubbish by a research lab.
It was not working due to two short-circuited rectifier diodes in the main power supply assembly (which off-course also blown the 1A fuse on the trasfo primary side), now I fixed it and it seem to work, or at least the display is working and it can execute calculations input from the keyboard. Its magnetic core memory still retains the last program loaded maybe 25 years ago...
It is a very nice piece of hardware and I would like to study it a little more in detail.
What I would like to test is the magnetic card reader, the D-shaped rubber wheel seem to be in very good condition, but I have no original card available.
I read somewhere that it should be possible to reconstruct a working card starting from plastic sheet and videotape, I'm not pretty sure it could actually work but I' would try anyway if I knew the card specifications.
Could someone in possesion of a original card give me the exact dimensions of it (including thickness) and the dimension/position of the magnetic bands ?

Thank you


Hello Paolo,

I would not advise to test your reader with something else than an original magnetic card.

Alternatively, you have mail :-)



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