Making an ATX Bench Top Power Supply

This is the easiest way to build a bench top power supply, I use an ATX computer power supply,A few parts from old electronics, and an ATX breakout board from Amazon. Other than waiting for the circuit board to arrive, this bench top power supply only took me an hour to build.

You can buy ATX breakout boards from Banggood, ebay, AliExpress, or Amazon.

The total cost of this project was $4.87, my time, and salvaged parts from old electronics.

I’m a measure twice and cut once kind of guy, so we will be testing the power supply several times as we go.

Salvaged Parts

ATX power supply from old computer.

Power cord from old computer.

Circuit board posts or spacers from old electronics.

Stick on feet from old electronics

1 x 1 amp buss fuse.

A 10 Ω 10 watt resistor if needed.

New parts

24 pin ATX breakout board

Tools

Phillips screwdriver

Side cutter

A brush to clean the dust out of the ATX power supply.

Center punch

3mm drill bit

Drill

Wooden block

I have 3 ATX power supplies, 2 x 24 pin and 1 x 20 pin.

There are two basic ATX power supplies, A twenty pin ATX connector and a 24 pin connector ATX.

The pin outputs are as in the following diagram.

On the label you will find the maximum currents for each voltage in and out of the ATX.

NEVER EXCEED THE MAXIMUM OUTPUTS or you could damage the ATX power supply.

I got my ATX breakout board from Amazon for $4.87, I could not build this circuit board that cheaply, unfortunately that board is no longer available. I checked this ATX breakout board on the 3 ATX power supplies I have. It fit the 2 x 24 pin ATX power supplies however it did not fit the 20 pin ATX power supply.

Amazon 1

It is important to check the output currents of the ATX. This 24 pin ATX breakout board comes with 5 amp buss fuses on the 12 volts -, 12 volts +, 5 volts +, and 3.3 volts +. so I had to swap out the 5 amp buss fuse on the 12 volt -, for a 1 amp fuse.

On an older ATX you may need to add a 10 Ω 10 watt resistor to the 5 volt output, however my ATX worked fine without one.

Although there are a number of different breakout boards putting together a bench power supply doesn’t vary much and can be done in a matter of a few minutes.

Some ATX breakout boards are 24 pins and 4 outputs, 5 volt USB, ground, 3.3 volts +, 5 volts + 12 volts + and a adjustable output 1.8 to 10.8 volts.

Amazon 2

Some ATX breakout boards are compatible with 20 and 24 pin ATX power supplies comes with 5 amp buss fuses on the 12 volts -, 12 volts +, 5 volts +, and 3.3 volts +.

Amazon 3

And some ATX breakout boards are compatible with 20 and 24 pin ATX power supplies, 24 outputs, and you have to complete the wiring adding fuses and conectors.

Amazon 4

Plug the ATX power supply into the ATX breakout board and connect to power.

Turn on the power.

The power LED should light up.

Test all the outputs with and without a load, the voltage shouldn’t vary by more than a volt.

At this point you can start using the bench power supply as is if you want.

If the ATX doesn’t power up check the supply power, connections, and the power switch.

If the ATX doesn’t stay on try a 10 Ω 10 watt resistor between a 5 volt line and a ground.

If none of these checks work try the ATX breakout board on another ATX power supply. If that ATX power supply works it was the ATX power supply.

Before you start unplug the ATX, even unplugged the capacitors can carry a charge enough to shock you badly. So take care as you go.

Remove the screws holding the case together and open the case.

Using a brush remove the dust and lint from the insides.

Using the side cutters remove the unwanted wires by cutting them as close to the circuit board as you can. You do not need to do more than that since these wires were not connected to anything.

Reassemble the case making sure you don’t pinch any wires and test all the outputs again. This is to be sure you didn’t damage the circuit board or cut the wrong wire.

The feet will help to prevent the power supply from sliding about and damaging any work surface. Since these feet have two sided tape just wipe any dirt off the ATX and stick them on.

Since the ATX power supply has short leads I will be mounting the ATX breakout board to the metal case of the power supply.

Mount the circuit board posts or spacers on the ATX breakout board.

Make sure the screws and posts do not cause a short.

I adjusted the breakout board on the metal case until I found a spot I liked. Conveniently there was a hole in the case just the right place and size.

Using my vernier calipers I scribed the case to find where to drill the other 3 holes.

I opened the case and placed the lid on a wooden block, this is to keep metal shavings out of the power supply and to support the lid so it wont collapse while I am working on it.

Using a center punch I marked the lid where I wanted to drill the 3 holes.

Keeping the lid on the wooden block I drilled the holes.

Compare the holes to the ATX breakout board’s mounts, this is the time to adjust any of the holes out of alignment.

Bolt the ATX breakout board to the lid of the ATX power supply.

Reattach the ATX power supply lid making sure you don’t pinch any wires.

Test all the outputs again to make sure you didn’t damage anything.

And you are ready to start using your ATX bench top power supply.