Way I do it is to go to the computer store, (or Staples, or Office
Depot, or Best Buy, or...) and say: got a power supply?

I have replaced the power supply, and now I want to repair the old one.. I
shouldn't have to throw out a $50 peice of equipment because a 25c part is
broken.. (spending a day or two finding the problem doesn't worry me)

The problem is that it still supplies +5V standby, but refuses to turn on (I
have a load attached and I do have the correct wires for PS_ON and ground).

No fuses are blown, and nothing appears or smells obviously burnt.. I was
told to check for open/high resistors near the large filter caps on the high
side, so I did and they both read the correct ~220Kohms.. there's two
diodes on the high side and both those are ok also.. what else should I test
?

Chris