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Repairing the card reader for a 1960s mainframe: cams, relays and a clutch

Posted on Tuesday, February 13th, 2018 in reversed, vintage by DP

p-1402-card-reader-600

Ken Shirriff writes:

I recently helped repair the card reader for the Computer History Museum’s vintage IBM 1401 mainframe. In the process, I learned a lot about the archaic but interesting electromechanical systems used in the card reader. Most of the card reader is mechanical, with belts, gears, and clutches controlling the movement of cards through the mechanism. The reader has a small amount of logic, but instead of transistorized circuits, the logic is implemented with electromechanical relays.1 Timing signals are generated by spinning electromechanical cams that generate pulses at the proper rotation angles. This post explains how these different pieces work together, and how a subtle timing problem caused the card reader to fail.

See the full post on his blog.

This entry was posted on Tuesday, February 13th, 2018 at 11:42 pm and is filed under reversed, vintage. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

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