I Turned A Computer Power Supply Into A Bench Unit, Just Like The Rest Of The World

Yep, that’s all I did. I had extra AT power supplies kicking around and needed more (i.e., didn’t have any) good 12V bench power supply, so I stuck in a switch, banana jacks, a 10-ohm stabilizing resistor, and finished it just in time to spend a few weeks running my Grandmother-in-law’s LCD monitor until she got a new one after the power brick croaked.

But now I have it back and can document it.

I started with an AT power supply because I had a couple kicking around; this particular model is a 230W from Sparkle Industries. Switching is easier with these than with ATX supplies, I just hacked in a big DPST power switch and I was ready to rock. Or Toggle. No parasitic power drain, no extra transistor thingy to make it work.

As you can see the wiring is a little messy. For 5V and ground posts I crammed three or four of the wires into a crimp terminal. The binding posts, handily, have extra nuts on the back end which are perfect for spade lugs.

The 12V line is a female disconnect that just fit on the solder tab for that jack. I also had to jump the fan power from there, the original 5V fan had been copped for something else.

I used a 10Ω, TO-220 load resistor on the 5V rail to stabilize the output like everyone says to. You can see I just screwed it to the case (photo 3) and it works great. Make sure the tab is isolated from the leads before you do the same thing.

The power light you can see in photo four. It’s just the warm glow of an LED stuffed in where it would light things up, without drilling another hole in the case.

And rubber feet complete the build with dignity.

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