IBM 5155 Power supply schematics or info

[Alberto Rubinelli - A2 Sistemi]

> I think I would check C3001, in case it's shutting the PSU down before
> it's properly started. Then look at the collectors of Q3002 to see if the
> thing is detecting an overvoltage.

The under voltage protection is always active :(
When power is applied, the collector of Q3001 goes high (about 4.5V)
immediatly, after about 0.5 seconds, the SCR is fired and the power supply
enter in protection mode.
During the short time of outputs presents, I have check the value (with
scope, multimeter in not enough fast) but they are of the correct value (+5,
+12, -5, -12) but I ignore the tolerance of the under voltage protection.

Maybe IC3001 or IC3002 defective ?

Thanks a lot !

Alberto

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