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Wednesday, April 7, 2021

CONTINUITY: Hewlett-Packard 9825T Repair Part 1: Power Supply

In January, 2021, Curious Marc's 1970s vintage Hewlett-Packard 9825 laboratory computer blew up when a single transistor in the power supply failed with a dead short from emitter to collector which placed 13 volts on the +5 power supply rail. This caused one integrated circuit on one of the boards to literally explode, with less apparent damage elsewhere the way to bet. The diagnosis and repair adventure begins with fixing the power supply.

Posted at April 7, 2021 14:41