This is just meant to go over the basics of building a lab power supply out of an old atx power supply. The first thing i will do is go over the basic pinouts & wire colours you will need to worry about.
Green - Power On to power supply
Gray - Power OK (for your status light)
Black - Common (ground)
Purple - +5v DC Standby (not used)
Orange - +3v DC
Red - +5v DC
White - -5v DC (removed in the 2004 atx power spec)
Yellow - +12v DC
Blue - -12v DC
Please note, that the -5v may not be there. It was eliminated in newer atx power supplies. Also that the negative voltages do not have a high amperage (they are limited to approx 5 amps or less
). A full guide to the 20 pin molex connector pinouts can be found here: ATX power supply connector pinout and wiring @ pinouts.ru
The first thing that needs to be done before you start hacking into the unit is to test it. I prefer to use an old hard disk. plug it into one of the molex connectors, and jumper the green wire to a black wire. This should give you a base load and allow it to start up so you can verify your voltages.
Once you have the supply tested, you can go about to hacking up the wiring. the first thing to look out for a smaller orange and red wires, these are for a signal reference, and must be connected somewhere to their respective wires, or the power supply will not operate, or could fry the voltage regulator.
So, as for building your case, and installing your binding posts, that is up to user preference, but i recommend attaching all the corresponding colored wires to their respective binding posts. it allows for a larger draw through the binding posts. How i did mine, was i twisted the green power on wire to a black common wire, and put a led & resistor inline to the black wire from the gray wire. Now depending on how lazy you want to be, you can either use a old hard disk for your base load, or use a 10w 10amp resistor across the 5v bus (between red & common). Without a load on the 5v bus, most of these power supplies will not give full voltage. Also make sure you have the smaller signal reference wires attached to your binding posts so that the power supply will regulate the voltage correctly, and that should be it
I hope this helps somewhat