While packing up my things to move house I came across an old ATX PSU that I forgot I owned. Rather than putting it in a box and getting on with packing, I figured I'd re-purpose it as a bench supply. There's plenty of write ups on the web about this, but I worked directly from the pinouts on Wikipedia.
Here's what the PSU looked like when I opened it up. As you can see, I have removed a fan from the back (front?) of the unit, this is where the bench supply outputs will go.
This is where the fan came from, I've placed a sheet of Sintra board behind the opening (covered with masking tape so it's easy to draw on). Notice the U shaped cut out (top left), this is where the original ATX wiring loom came out, but I'll be using it to mount a switch.
Here's the openings marked on the Sintra
Holes cut out for the outputs and switch
Here is everything fitted to the Sintra panel. The outputs will be wired up as 3.3V on the top left, 5V top right and 12V at the bottom.
I have no photos of the wiring as the space to too tight to get any good shots, but it is fairly trivial. Hook the yellow wires up to 12V output, red ones to the 5V output and orange ones to the 3.3V output. Make sure to hook up as many ground wires to each ground output as you have live wires, to ensure maximum current capability. Hook up the green wire to the switch, and ground the other terminal.
Here is the finished product (currently without labelled outputs), notice the addition of an LED between the top outputs. This is just to serve as an obvious indication that the supply is on. I also added the intake hole on top, as removing the 2nd fan was starving the supply of cold air.