Delete comment from: Ken Shirriff's blog

Michele said...

Most interesting. And great work. The power supplies always seemed to cause trouble, even back in the day. One of my 12 V supplies suddenly stopped working one day last year. Turns out it had a bad 390 pF silver-mica cap that took out the 680 ohm 5 watt resistor next to it in the Q3/Q4 inverter drive. The resistor was fried to a crisp. Replacing those two parts restored proper operation. I tested the big cans and they were still good so I just left them there.

Those power supplies are a real pain to work on, with their convoluted folded-up origami layout.

May 8, 2017, 1:25:25 AM

Posted to Restoring Y Combinator's Xerox Alto, day 1: Power supplies and disk interface