HP Forum Archive 18

[ Return to Index | Top of Index ]

HP 9100B magnetic card Message #1 Posted by Robert Bennett on 26 Feb 2008, 12:48 a.m. Does anyone have a (functional) programmable magnetic card they are willing to part with for an HP 9100B; and any information about servicing/repairing the card reader, or technical details about the cards? Thanks.

Re: HP 9100B magnetic card Message #2 Posted by Tony Duell on 27 Feb 2008, 2:13 p.m., in response to message #1 by Robert Bennett What exactly do you want to know? I've worked on the 9100B, and have a fair idea of how the card reader works. I assume you've got the unofficial schematics (for example from the Australian Site). The card reader has a 4 track head, and stores 6-bit keycodes. One track is a clock track, handled by the reader electronics. The other tracks store the keycode as 2 3-bit words, the odd bits and even bits are separated. It talks to register 2 (main accumulator) in the 9100, the interface is not _quite_ the signals on the external connector. And yes, it does make use of the fact that the register is made of JK flip-flops to load the 2 sets of bits. The main problem with the reader is that the drive roller decays with time (what a suprise!). The original roller, I believe, had a flat on it, but a circular one will work, it's just harder to push the cards in. A 1" (outside diameter) O-ring will work, but the problem is fixing it to the hub. I ended up pulling the old hub off the motor using a special home-made puller tool, and machining a new hub from 7/8" brass rod.

Re: HP 9100B magnetic card Message #3 Posted by Robert Bennett on 27 Feb 2008, 6:35 p.m., in response to message #2 by Tony Duell Tony, Thanks, This is the sort of info I was looking for, since the roller on the unit I have is just as you described. Do you know how much data / instructions can fit on a single card? Regards and thanks for your help.

[ Return to Index | Top of Index ]

Go back to the main exhibit hall