Repairing a 1960s mainframe: Fixing the IBM 1401's core memory and power supply

1 · Ken Shirriff · Dec. 24, 2017, 5:13 p.m.
A few weeks ago, I wanted to use one of the vintage IBM 1401 mainframe computers at the Computer History Museum, but the computer wasn't working.1 This article describes the multi-week repair process to get the computer working again. The problem started when the machine was powered up at the same time someone shut down the main power, apparently causing some sort of destructive power transient. The computer's core memory completely stopped working, making the computer unusable. To fix this we h...