Ah no! This one was driving me mad for a few weeks as well. I was close to giving up on it too.
Well here's what I had to replace to get it working again.
Symptoms: low voltages on start-up. Voltages stabilise after a while and computer boots and works OK after that.
Solution: replace optocoupler CNY75GB or replace with CNY75B. I found other CNY75's don't work. Tried CNY75A and no good. Needs a high CTR (coupling transfer ratio) of about 100-200% it seems.
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