Converting a Computer Power Supply to a 12-Volt Power Source

I find myself with a frequent need for 12-volt power supplies, and I also have lots of old computers lying around. A few years ago I converted one for model airplane use by installing a female 12-volt SAE jack, just like the cigarette lighter in most cars. I was converting this one for another purpose, but the idea is the same.


This is not a typical consumer-level project. If you are learning by trial and error, that is your own risk to assume, and I won't accept any responsibility for the use or misuse of the information on this page. Power supplies like this have capacitors that can remain energized even after you unplug the power source. Be smart and careful when you are working on power supplies.

In the first picture below you can see the information about the particular supply that I used. Yours may vary in color codes or other areas, especially in the circuits that control the on-off switching. Completion of this project will require a phillips screwdriver, a multi-meter, a soldering iron, soldering supplies including heat shrink tubing, and a few other tools like a knife and wire cutters.

In the second picture you can see what the business end looks like when you open it up. The yellow leads are +12 volts, and the red are +5. These are the most commonly used by the computer, so there are lots of them. The black is a common, and there also some -5 (white), -12, and +3.3 (orange) leads in there, but I haven't found any use for them. If you are currious about which ones they are, just leave them and hook them up accordingly.

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My first step was to cut the wire ties and remove the fan. This gave me a little bit more room to work. I removed the circuit board so that I could get to the solder side of the board. Rather than cut the wires I didn't need, I just removed them from the board entirely.

In the second picture below you can see how I've started to remove the red wires. Just melt the solder and pull, and they come right out. Make sure that you haven't inadvertenly let any of the melted solder short any other circuits on the board. I would suggest leaving all of the leads for whichever voltages you intend to keep, so that you can deliver the most current to your desired circuit.

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In my case I had to connect the blue and brown wires together to convince the power supply to turn on without the switch that was originally part of the computer.

DSC_4817.JPG DSC_4822.JPG If you don't want to have wires hanging from the box, you could install female banana plugs, or an SAE jack as I mentioned earlier. Good luck, and don't electricute yourself.