Simple Computer Power Supply Tester


Simple Computer Power Supply Tester

This Comment/How-to is a quick guide to build a 20 pin computer power supply tester out of parts from old computers and PSUs. The tester will also work on power supplies that have the 20+4 pin connecter. You can use this method to make a 24 pin PSU tester as well. Similar units sell for around $15-$20 but you can make one for pennies if you have the parts laying around like I did. The inspiration for this came when my friend gave me his old dead tester after he bought a new one.

Step 1:

Gathering the Materials

This Comment/How-to is meant to help save you money and keep people from wasting resources. All the parts I used (except the heat shrink) came from an old computer. This is just one of many things that can be built entirely from recycled components. I intend to use every piece of material from this pc. Every computer that goes bad i take apart and strip out all the working components before sending the rest off to be recycled or disposed of properly.

Be careful de-soldering! If you heat up the pins in the power connector too much it will melt and deform the plastic. I have unwittingly done this before.

button or switch (as long as it is not momentary)
2 wires (same length, however long you want it)
20 (or 24) pin connector socket

Step 2:

Finding and removing the unnecessary pins

For this Comment/How-to you only need 4 of the 20 pins on the MOBO power connector.

The pinouts for 20 and 24 pin connectors can be found here and are very helpful:
20 pin -
24 pin -

The only pins we will use are (on the 20 pin) pins 7 and 8 which are Ground and Power OK respectively, and pins 13 and 14, Ground and Power On. The others can be removed by pushing them up through the bottom. Don't throw the unused pins away yet. If you mess up you may need them.

From here on I will be referring to the number of the pin for 20 and 20+4 pin connectors so if you need a 24 pin look up the pinout on the link.

Step 3:

Attach the switch

The switch you will use to turn on the power supply is soldered to the two wires. After attaching the wires to the switch, attach them to pins 13 and 14 of the connector.

Step 4:

Attaching the indicator LED

Finally, the LED is soldered onto pins 7 and 8. Make sure that the positive side of the LED is on pin 8 and the negative side is soldered to pin 7, Ground. After i soldered it i bent it upward so it wouldn't catch on anything and mess it up.

Step 5:

Test your tester

Now that you have a completed PSU tester in your hand, my suggestion is to use it first on a power supply that works. Unhook everything from the power supply first (except the power cable of course). Take sure the switch on your tester is in the "OFF" position and attach the tester. Once it is attached, flip the switch. If your LED lights up, you have a working power supply! If your power supply has a fan in it and you notice the fan is spinning but the LED isn't lit, you have placed the LED on the wrong pins or it is poorly soldered (or you have a faulty LED).

And there you have it, a computer power supply tester made from recycled computer parts!


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