Gregory's ServerI checked the computer's driver boards; each board has flip-flops to drive two coils. Like all the 1401's circuitry, the boards used germanium transistors. Silicon hadn't caught on yet. The boards were pulling the lines to ground okay, but I didn't see -20V from the punch. 6/9
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 A thick cable connects the 1402 punch to the 1401 computer with 80 wires for the electromagnets. Inside the computer, "paddle cards" connect these wires to the computer's circuits, in groups of 16. I spotted a paddle card that had come loose. This was our problem! 8/9 Pushing the paddle card back into place fixed the punch. An easier fix than most! Now we can use the punch to create new card decks for demonstrations. You can see the system in action on Wednesdays and Saturdays https://twitter.com/ComputerHistory in Mountain View, CA, so stop by. 9/9 @kenshirriff I was there on Thursday! Hope to be able to stop by & see it it in action before I leave SF! |
We checked the punch and it was generating -20V pulses correctly. So where were they getting lost? By measuring continuity at various points, we determined that the problem was on the 1401 computer side. 7/9