How to Turn on a Computer Power Supply

How to Turn on a Computer Power Supply

Computer power supplies are easily available in the market and they make for decent 12 volt or 5 voltpower supplies. However, standard power supplies are not built to turn on when they are not connected to a motherboard.

To test a PSU, you may need to know How to turn on a computer power supply. So, if you want to turn on a power supply without it being connected to the computer, you need to find a way to do it. This is actually much easier than you think but you should be careful.

Connecting to Motherboard: How to Turn on a Computer Power Supply

The main reason why a power supply won’t turn on unless it is connected to a motherboard is to prevent the damage of computer components if the plug is not connected properly. However, if your intention is to test the components or you want to include a lot of hard drives in a case to increase the capacity of your office server, there’s a way to turn on a computer power supply without the motherboard installed.

To carry out this bypass procedure, you need a single-pole switch and some wires. You may get an inexpensive light switch which may be flipped on and off easily. However please ensure that the switch is easier to mount. Now follow the steps mentioned below:

Cut two same lengths of wire which should have the right length to easily connect to the switch and the 20-pin power connector coming out of the power supply.

Now, remove the insulation from one end of the two cut wires. You must leave enough stripped wire to be able to easily tie it around the switch’s terminal. Now remove insulation from the other end to connect them to the terminals on your PSU’s 20-pin or 24-pin connector.

To connect the wires, simply loosen the screw on one end of the terminal and wrap the longer part of stripped wire around it. Now use a screwdriver to again securely tighten the terminal. Repeat the same process using the second wire for the other terminal.

Set the switch to ‘off’ and then unplug the power supply from the wall. Now hold the 20- or 24-pin of your power supply with the terminals facing on your side. The plastic locking piece should face upwards and the flat edge should face downwards.

You may now insert one wire from the switch that is located in the third terminal on the top row. You should be able to see two empty terminals on the left hand side. Now insert the other wire inside the terminal which is to the right side of the first wire.

So, on the top row you must have two vacant terminals, two terminals with wire passing through them, again six to eight vacant terminals. The bottom row in the power supply should be empty.

Now you need to plug the PSU back into the wall by mounting it and then turn on the switch if you locate one.

Set the switch you have installed to ‘on’ mode and then turn on the power supply. Your computer power supply is now ready to use without the motherboard. You may use it to power different types of devices or use it for testing.

These are the things needed for the above steps:

  • Wire
  • Switch
  • Screwdriver
  • Wirecutter

Important tips and advice

After you have connected the wires from the switch to the power supply, you need to confirm that it’s working fine. Once you are sure that the PSU is working as expected, you can solder the wires or use electrical tape to secure them firmly in place.

We strongly recommend that you avoid working on the power supply when it is plugged in. This will not only increase the chances of damaging the power supply but the other components may also be electrocuted.


Power supplies are typically designed to work only when they are connected with a computer. However, when there’s a problem in the PSU and you need to troubleshoot, identifying the issues may be difficult when it is attached to the motherboard.

Testing the different components of the PSU can be possible only when you take it out of the case and turn it on without the motherboard. We hope the steps above help you with the process. However, always be careful when dealing with electricity and ensure that the power supply is switched off before working on it.

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(1) comment

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