3 Ways to Tell if Your Power Supply or Motherboard Is Bad

Easy tests you can perform yourself to diagnose your CPU

Co-authored by Luigi Oppido and Sam Browning

Last Updated: December 22, 2024 Fact Checked

Identifying a failing component in your computer can be difficult, especially when different components malfunctioning lead to the same symptoms. Luckily, there are specific methods you can use to check that your power supply and motherboard are working as expected. This wikiHow article will teach you how to test both your power supply and motherboard for faults.

Signs Your PSU Is Bad

Your power supply unit may be bad if your computer won’t turn on, it keeps restarting or showing a blue screen, makes strange noises, or has a burning smell.
Use a power supply testing unit or the “paperclip test” to determine if your PSU needs repair.
On the other hand, your motherboard may be bad if peripherals like your mouse and keyboard are unrecognized, your computer boots slowly, or there’s a burning smell.

Method 1

Method 1 of 3:

Using the Paperclip Test

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If your computer is not turning on, it continually restarts or blue screens, or it makes strange noises or is giving off a burning smell, you could have a failing power supply unit. ^{[1]
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Set the switch on the back of your PSU to “Off”, then unplug it from the wall outlet. ^{[2]
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Most cases have a side panel that can easily be removed to access the components of the computer.
If you are not as familiar with computer components, consider taking a picture of your computer to help you remember where each PSU cable connects.
You can use this paperclip to make your PSU think it has been turned on, allowing you to test it. ^{[3]
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The 24 pin connector plugs into the motherboard, and it is the largest of the PSU connectors. Additionally, there should be only one green pin, while there are a number of black pins. ^{[4]
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By connecting the two pins with a piece of metal, you will essentially be able to jump start your PSU when you plug it in and turn it on.
Be sure to check one last time that all other devices are disconnected before turning it on to properly test your PSU.
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Check to see if your fan is moving. If your fan is moving, your PSU is turning on. Otherwise, unplug your power supply, double-check your paperclip placement, and run the test once more. If the fan still does not move, your PSU is probably dead.
- Even if your fan is moving, your power supply might not be outputting the correct power levels. To be certain it is working as intended, test it using the next method.

Method 2

Method 2 of 3:

Using a Power Supply Testing Unit

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They can be purchased online or at an electronics store and are relatively inexpensive.
This will take away any residual current and help you avoid getting shocked.
The 24 pin connector will likely be the largest of the PSU connectors. ^{[5]
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Expert Source

Luigi Oppido
Computer & Tech Specialist

Expert Interview. 13 November 2020.}
If there is a button on your power supply testing unit to turn on your PSU, press it. Otherwise, your PSU should automatically turn on, and you should begin seeing readings on your power supply testing unit.
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Check your voltages against their acceptable ranges. There are four key measurements you should look for, each with their own acceptable range of variation. If any of the measurements are outside their acceptable ranges, the PSU should be replaced. ^{[6]
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- +3.3 VDC (within +/- 5%)
- +5 VDC (within +/- 5%)
- +12 VDC (within +/- 5%)
- -12 VDC (within +/- 10%)
If your 24 pin connector is outputting power properly, work your way through each of the PSU’s cables, turning it off and unplugging it between each test. If all the cables are outputting properly, your PSU is likely working!

Method 3

Method 3 of 3:

Testing Your Motherboard With POST

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If your computer is not recognizing peripherals like your mouse and keyboard, your computer boots more slowly than usual, or you smell something burning, your motherboard might be dying. ^{[7]
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Set your motherboard on the edge of a flat surface. If you are using an external graphics card, this will allow it to sit on the motherboard without damaging any overhanging prongs.
- Additionally, avoid static electricity as much as possible! Ideally, use a surface like wood or glass, and do not stand on carpet.
Depending on your motherboard, you may have to unscrew some brackets to install your CPU. Your CPU should seat properly without any force. ^{[8]
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While a cooler is not necessary for this test, if you are building a new PC and the test is successful, already having your cooler installed will take away another step in the process.
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Mount your RAM . Be sure to align the small notch at the bottom of your RAM with the notch in your motherboard. Once the notches are in alignment, use a small amount of force to push down until you hear a click.
- If you are using multiple sticks of RAM but are not filling all your computer’s available slots, refer to your manual for optimal placement.
Install your graphics card . Many Intel CPUs and some Ryzen CPUs have GPUs built in, so it may not be necessary to connect an external graphics card depending on your build.
This method requires a working PSU, so be sure to test it using the two methods above before proceeding. Your PSU should connect to the motherboard with a 24 pin connector, while the pins in the graphics card connector will vary. ^{[9]
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Most commonly, the connectors on the motherboard will be HDMI and/or DisplayPort. Cables will likely be included with your monitor.
You should now see lights appearing on your motherboard.
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Check that your computer boots to the BIOS settings. If the BIOS screen does not appear on your monitor, something has gone wrong. Try checking that all components are properly installed and connected and try again. ^{[10]
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- If you are hearing a series of beeps, that is a beep code that represents a specific error. ^{[11]
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- Your computer performs a POST each time you turn it on, so if your motherboard is already installed, turn the computer on. If it boots properly and there is no beep code, but you believe something is wrong with your motherboard, consider consulting a professional.
- Often, the easiest way to determine you have a bad motherboard is checking every other component in your computer. After a failed POST, ensure all other components are working before assuming your motherboard is nonfunctional.