Without a power supply, even a high-end desktop PC is just a collection of computer parts! This crucial component provides the necessary electrical voltage to your CPU, GPU, motherboard, and more. Fortunately, most of today's power supply units are highly reliable, and many PC users can go their whole lives without having to change one out.
Sometimes, however, you might need to test your power supply unit (PSU) to ensure that it's in good working order. Testing your power supply can be a key part of troubleshooting certain PC issues, or it might be a precautionary measure when you're installing a power supply in a new PC.
Whatever the reason for testing, it's important to get familiar with the best practices of how to test a power supply before you start. Micro Center's experts have tested more than a thousand PC power supplies in our time — so let's jump in and learn about the surprisingly easy ways you can do it yourself!
What Is a PC Power Supply?
Your PC's power supply is the part that converts AC power from your wall outlet into DC power that your computer can use. In most desktop computers, the power supply is a box-shaped unit with a built-in fan, usually installed near the bottom of the PC case. One side of the power supply has a three-prong grounded outlet that connects to wall AC power, and the other has a series of multi-pin connectors that connect to the motherboard, GPU, and other components.
Laptop power supplies work differently, since they use both a battery and a charger to provide power. If your laptop is experiencing power-related problems, look into how to check your battery health and how to test your laptop charger using a multimeter. (Don't forget that Micro Center also offers easy laptop battery replacement services!)
When Should I Test My Power Supply?
Here are three times that you should definitely test your power supply:
- You've bought a used power supply and want to verify that it's in good working order before installing it.
- You're planning to reuse a PSU from an old PC and want to ensure it still works well.
- You're noticing problems with your PC that could be caused by the power supply, and you've ruled out other common causes.
However, some experienced PC builders swear by the practice of testing every PSU before installation, even a brand new PSU from a reputable manufacturer. Testing is a relatively quick job with the right tools, so if you have them on hand, it can be worth it to go ahead and knock it out — even if the risk of getting a defective new-in-box PSU is quite small.
Signs You Might Need to Test Your PSU
When should a PSU test be part of your troubleshooting process? These are some common signs that a PSU test might be in order:
- Your PC won't turn on, or it randomly shuts off and/or reboots without warning.
- Your system's video output is freezing or crashing, especially during demanding tasks like gaming or video editing.
- Your PSU's fan is running significantly louder than normal. (Generally, you want to hear only a low hum, with no loud grinding or buzzing sounds.)
- You've noticed a burning smell coming from your PC. (If you're experiencing this, unplug your PC right now. It could mean your PSU is at risk of starting a fire.)
- You're experiencing any kind of mysterious issues that you can't attribute to other sources like new components or software updates.
That said, other factors can come into play, and it can be worth checking these first before you decide to troubleshoot your PSU specifically.
Things to Check Before You Test Your PSU
- Look up troubleshooting guides for the specific issues you're experiencing and try other solutions first. For example, if your graphics card is crashing when playing demanding games, be sure that it's updated with the latest drivers.
- Make sure that all of your cables and connectors are fully seated in their slots.
- If the computer won't power on, try connecting it to a different outlet (or directly to the wall outlet, if you're plugged into a power strip).
- If you're using a modular PSU (one on which all of the cables detach), make sure you're not mixing and matching cables from other PSUs.
One final extremely important note before we get to the testing process: Do NOT open the casing on your PSU or otherwise disassemble it in any way. The internal components of a PSU are not designed for user servicing, and the high-voltage components can deliver extremely dangerous electric shocks.
The Jumper Test
First up is the “jumper test,” an extremely basic test that will tell you if your PSU is capable of powering on. This test can seem a little scary, since it requires you to insert a piece of metal into your power supply's pinouts, but it's quite safe so long as you follow the directions.
Here's how it works:
- Unplug your PSU from all of your PC components and from the wall outlet. If your main power cord and/or your 24-pin motherboard cable detach from your PSU, leave those attached.
- Find a metal paper clip and bend it in half, forming a U-shape.
- Take the end of the 24-pin ATX cable that plugs into the motherboard, holding it with the clip facing you. Find the pins for the black wire (the ground wire) and the green wire (the main power supply) on your motherboard cable. The black wire should be third from the right, and the green wire fourth from the right. (Pinouts on small form factor power supplies may be different, so check your PSU's manual first.)
- Make sure that the power supply's main power switch is off and that it's unplugged from AC power. Then, insert both ends of the paper clip into the pin sockets — one to the green wire, one to the black.
- Plug the PSU into the wall outlet and turn on the power switch.
- If the fan begins to spin, your PSU is at least functional enough to power on. Note that it's OK if the fan starts running and then stops after a second. Many modern PSUs will only run continuously with a steady load from the motherboard.
The downside of this test is that it tells you only one thing: whether or not the PSU will power on. If you're testing a brand new PSU, many PC builders will consider a paper clip test good enough to go ahead with the installation. To investigate the actual functionality of your PSU, you'll need to go a little deeper and test the individual pinouts.
It is important to note that the jumper test is not a foolproof way to test a PSU. There are some cases where the PSU may pass the jumper test but still not be working properly. However, the jumper test is a good first step in troubleshooting a PSU problem.
Here are some safety precautions to take when doing the jumper test:
- Make sure that the PSU is unplugged from the wall outlet before you start.
- Do not touch any other pins on the PSU while you are doing the test.
- Be careful not to bend or damage the pins.
If you are not comfortable doing the jumper test, you can take your PSU to one of our qualified technicians to have it tested.
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Testing with a Multimeter
A multimeter is a handheld tool used to measure electrical forces like volts and amps. Electricians use them constantly as a diagnostic tool, but they're also useful for pinpointing electrical problems with your PC components. Multimeters are relatively inexpensive and easy to find online (check out our collection of multimeters and test equipment here.)
The array of options on a multimeter seems complicated at first, but the process is actually pretty simple:
- Turn off and unplug your PSU.
- Choose the DC voltage option on your multimeter. Its symbol is a capital letter V accompanied by one solid and one dotted line. Make sure the black and red leads are connected to their corresponding slots on the multimeter.
- If you've already performed the paper clip test, keep the paper clip in place. If you haven't, follow the above instructions to get it connected to the power-on and ground pins.
- Connect the meter's black lead to any of the grounded pins on the connector. (There will be several, and they should all be labeled COM and usually have black wires.) Connect the meter's red lead to the pin you want to test.
- Check the voltage displayed on the multimeter's screen and then compare it to the correct voltages from a standard ATX pinout chart. It's OK if some voltages aren't exactly on the money, but if they're off by more than approximately five percent, it's a sign that something is wrong with your PSU.
- Continue to compare voltages until you've tested all of the pins or found a faulty one.
Testing with a PSU Tester
Maybe this all sounds a little too complicated, but you still need to know whether your PSU is working correctly. Fortunately, there's an easy and relatively inexpensive all-in-one answer, which is to use a dedicated power supply tester.
PSU testers simplify the whole process by allowing you to plug in the entire 24-pin ATX connector at once. Once it's plugged in, turn on the power to your PSU and then the power to the testing unit. The digital LCD readout on the PSU tester will display the voltages of the different pins. (Again, check a standard ATX pin chart to determine whether your voltages are correct.)
If you regularly build and/or repair PCs, a PSU tester can be a worthwhile investment. Reliable models are available for under $50, and like multimeters, they're handy to have around.
Using a Known-Good Power Supply
If you're troubleshooting a potentially faulty PSU and you have another power supply on hand that you know is in good working order, you can test whether it's able to power on your PC. This is a somewhat labor-intensive method, since you'll need to connect it to your PC components and verify that your known-good unit has the specs to power everything in the first place.
The upside of this method is that it makes it easy to tell if your PSU is the problem. If the PC works without issues when the known-good PSU is installed, it's a near-certain indicator that you need to replace your old unit. There's also the flipside option: You could try installing the PSU you want to test into a known-good PC. However, this risks damaging your PC components if the PSU is faulty, so it's not recommended for most users.
My PSU Is Bad: Now What?
You've run the tests, and the news is bad: Your power supply is shot. So what do you do now? Having a PSU repaired is generally more trouble than it's worth. Few technicians will perform the work, and today's power supplies are inexpensive enough that it's more cost-effective simply to replace one.
Keep these tips in mind when you're selecting a new power supply for your PC:
- Remember to calculate the power requirements of your PC components, and choose a PSU with some headroom in case you want to upgrade parts such as your GPU later. (Our PC builder tool can help!)
- Choose a power supply with at least an 80 Plus Gold rating. This helps ensure your PSU operates efficiently without wasting excessive amounts of power.
- Stick with power supplies from recognized brands with good reviews. The no-name PSUs that some big eCommerce sites sell at bargain-basem*nt prices are often manufactured with little regard for quality and safety, and some can even damage your PC.
Shop Power Supplies from Micro Center
Micro Center is a one-stop source for PSUs, testing supplies, and everything else you need to get the very best performance from your PC. Our PC experts are always happy to help. Get in touch with us online, or walk into any Micro Center store nationwide for in-person assistance!
