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

Reverse-engineered schematic of the IBM 604’s TR-3 module. (Credit: Ken Shirriff) Taking a break from ogling microscopic features in Intel’s semiconductor processors, [Ken Shirriff] is back to instead poking at decidedly macroscopic pluggable modules from the 1948 IBM 604 Electronic Calculator. This time around it’s one of the so-called trigger modules in the form of the TR-3 , which uses a flip-flop circuit to implement the timing signals and pulses that made the 604 work.