STB #18 – HP (Hewlett Packard) Power Supply 721A from the early 1960s

A look at and tear-down of a couple of HP (Hewlett Packard) Power Supplies Model 721A from the early 1960s. The date on the PCB silkscreen is 1959. I believe this was HPs first transistorized power supply; it also featured over-current protection. Based on what I’ve read these sold very well; I’m guessing part it was the novelty of having a new-fangled transistirized power supply on the bench!

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