Energizing a Vacuum Tube Flip-Flop Module of the IBM 604

Ken Shirriff has reverse-engineered and powered up a flip-flop circuit from a nineteen forty-eight IBM six zero four calculator. Hackaday reports that the TR-3 trigger module uses a dual triode vacuum tube to generate timing signals, and Shirriff managed to make it work reliably — though it required careful tuning to stay stable. The design was eventually replaced by more reliable transistor logic, a shift that became standard in early computers.

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