PreferLinux :
I disagree. That may well be the case on the PSU in question, and also many older ones, but it is not the case on a lot of modern ones. Also, some PSUs specify the loading required on each rail, and often it is required on the +12 V rail and no others.
Thanks to you and pjmelect for great input. I think I’m sitting here with two bad power supplies.
Tested with a hard drive as a load. Nothing. Didn’t quite know how to get the 12v load so I installed the power supply in the computer and connected all the plugs except the 24-pin plug. Shorted pins 15 and 16. Still got nothing.
Get a reading of 5 volts at pin 9. Get a reading of 4.6 volts at pin 16 before shorting it out. Nothing else.
The only sign of life is that if I short pins15 and 16 after the power supply is plugged in, the case fan starts for a split second.
Tested both power supplies with same results.
Thanks much for everybody’s input. Guess I didn’t do much to resolve whether you need a 5 volt or 12 volt load, or both, to get a good test.