The best way to test any power supply is to put a load on it, like a hard
drive and a fan, and then turn it on. Computer power supplies are
sophisticated switching power supplies. This means, that they output DC
power as it is demanded, rather then outputting maximum power levels when
you turn it on.

When testing an ATX power supply, it will be necessary to turn it on with
the signal wire. Take a paper clip and make a U out of it. Put one end into
the motherboard power connector block at the GREEN wire = signal wire. Now
put the other end into any black wire = ground wire. You can now power it
on normally by plugging it in to AC power, or using a paddle switch on the
back of the PS. Better quality ATX power supplies usually provide the
paddle switch.

If the fan takes off, and you hear the hard drive spin up, then it means
you have power. At that point put a meter on one of the power plugs. The
yellow wire should be at 12 + volts DC and the red wire should be 5 + volts
DC.  If this is the reading you get, then you know that the power supply is
operating within specs.

However, the PS could still be failing under certain conditions. For
example, ...under a heavier load, ... or after it has been running a while
and has heated up. With these sorts of failures you really have to catch it
in the act, or use a process of elimination to pinpoint the source of the
problem. Often, in order to solve a problem where the PS hasn't just died,
you have to swap the PS out and see if the problem goes away. If the
problem is still there, then you know it isn't your power supply.

Rode
The NOSPIN Group
http://freepctech.com

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