jaclaz, on 22 July 2010 - 01:40 PM, said:
Please take note that some older/cheaper PSU did/do not handle correctly being powered on without an even minimal amount of power being drawn from the 5V or 12V lines (or both).
Now I must say that I never got a PSU in my hands that didn't power up unless it was bad, read, already going out or a very bad design.
jaclaz, on 22 July 2010 - 01:40 PM, said:
The paper clip is of course valid for ATX PSU ONLYand NOT for AT, since you mentioned having some "vintage" machines, be aware of the problems that you may find.
Well, there are exceptions for sure, but when we talk about onboard USB 2.0 I don't believe I have seen anything not using ATX power

.
jaclaz, on 22 July 2010 - 01:40 PM, said:
With all due respect for the advice given before, DO NOT power on a PSU NOT connected to something, of be ready and VERY quick in switching it off if needed (typically they would make a whistling sound) if you keep them powered on and they "whistle" they will simply BLOW

in a matter of several seconds.
The whistling sound you are talking about you hear when there is a short circuit or a bad circuit, again, I still have to find a PSU that blows up by itself if there is no load.
jaclaz, on 22 July 2010 - 01:40 PM, said:
Measuring the voltage of a "disconnected" switching power supply may anyway give "false" results, I've seen too many seemingly good PSU's that simply failed to work when some power was drawn from them to trust anyone, in any sense, a test of a PSU not connected to "anything" may be a waste of time.
Correct, but we are talking about the 5VSB line and that should be around 5V, always, even when there is no load on the USB.
Just my 0.02, but I could have been wrong with the last 2000 different brand and model PSUs I tested

. Ow, by the way, PSU testers are cheap these days.
jaclaz, on 18 July 2010 - 09:02 AM, said:
Cool stuff, and cheap!.