[Anthony B]

I Had an old computer lying around in the garage and I pulled the Power Supply - a 115/230 Input or with a 3, 5 and 12v output - on side it said black/yellow = 12V - however I could only read 5.4v no matter across which colour leads I read them - red/black/back/yellow.

But as it is a computer P.S. it has about 100leads coming out the back end in various size plugs.

So advice I got is:-

First read this:

Wikipedia on P.S.

-scroll down to the PSU section
-bridge pin 16 [power on (green wire) ] to any black [ground] wire. this allows the PSU to work.
-You can just cut the wires and solder or even add a switch.
-the yellow wires are 12v

I did as advised by Nightrider on SFI - and voila it worked: