Baron wrote:

Bob Larter Inscribed thus:
Eeyore wrote:
Michael Karcher wrote:
larya wrote:

How can I turn the power supply 'on' at the power supply?...
If it's ATX, ground the PS_ON pin.

See Wikipedia for Pinout.

Beware. It may not regulate properly with no load on the 5 or 12 V
output.

On every PSU I've tried it on, the fan seems to provide enough load
for the voltages to be okay.

A lot of the better ones have suitable loading built in ! More often
the PSU wont start up if it requires a minimum load, though some will
but don't regulate the output voltages properly. The regulation is
done with reference to the 5v rail, so that is the one that should be
loaded. Its wise to play safe and stick a load on anyway. I use a 10
ohm 10w resistor wired into a spare connector so that I can add or
remove it as needed. I also have a LED wired as well so that I
remember to switch off when working on an open case.

I've heard of some where the feedback is taken as a mix of BOTH the 5V
and 12V loading. No guarantees though.

I agree that 'some' load on the 5V is likely best.

Graham