Checking new PC power supply

[HarryA]

I have a new power supply that I would like to check before
installing into the computer. On bench testing it I get no
voltage at all. Is thid correct? I am thinking that perhaps
there is some type of interlock so you only get voltage
when it is installed?

thanks in advance.

[Alex Tsekenis]

Have you switched on the power supply from the motherboard connector? Is it a 24 or 20 pin (the main connector) PSU? Does the fan rotate?

http://www.ochardware.com/articles/psuvolt/psuvolt.html

There are also cheap PSU testers...

http://www.frozencpu.com/resource/r12/Using_a_Power_Supply_Tester.html

[jcizek]

You must "turn on" the supply within the connector if this is a modern ATX type power supply.  Usually (take that at face value, lots of power supplys are differernt) it's the skinny blue wire in the motherboard harness that must be grounded to turn the supply on.  You will also need to load the 5 Volt line (red wires on the output) with a  load for it to regulate properly. 
Alex is right, a power supply tester is the safest way to test them, and keep from blowing up a brand new supply!  -James

[HarryA]

Thanks guys. That's what I needed to know  :)
I made a tester out off a 12 v brake light and
a 6 volt one  ;)