Gregory's ServerHow much trouble can one wire cause? The IBM 1402 Card Reader/Punch (1959) was a workhorse of the punch-card era, speedily reading 800 cards per minute. But the museum's card reader occasionally crunched cards and jammed, interfering with the demonstrations. 1/8
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To debug the relay circuits, I built a Hall-effect sensor to magnetically determine if the relay was activated or not. https://twitter.com/Curious_marc helped me build the sensor and mounted it in a stylish soap dish. The sensor displays the relay status over time on the oscilloscope. 3/8  @kenshirriff I have the same 'scope as this, though my hardware lab is missing a soap dish at all, let alone one as stylish as yours. Clearly I shall need to correct this oversight. @kenshirriff Oh my. Is this how professional electronic equipment looked on the inside in those days? Such haphazard assembly of components.  @kenshirriff |
Debugging the card reader is tricky. The card reader is controlled by numerous relays, electromechanical switches that are prone to malfunctioning if their switch contacts get dirty. The photo shows rows of relays above a jumble of diodes and resistors. 2/8