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How Do I Test the Power Supply in My Computer?

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Photo of a Sentey Bxp450-ps Power Supply

Sentey Bxp450-ps Power Supply (NEVER Open a Power Supply!)

© Sentey Inc.

Testing a power supply is an important step when troubleshooting many issues, most obviously when your computer is having trouble starting.

However, a failing power supply can often be the cause of problems you might not expect like random lockups, spontaneous reboots, and even some serious error messages.

Ask any computer repair professional and he or she will probably tell you that the power supply is the most common piece of hardware to fail in a computer.

In my experience, the power supply is very often the first thing to fail as a computer ages.

"How Do I Test the Power Supply in My Computer?"

You can test a power supply yourself manually using a multimeter (method #1) or you can purchase a power supply tester to perform an automatic PSU test (method #2).

Both methods are equally effective ways of testing a power supply so which one you choose is completely up to you.

Here's some more information on how to test your power supply with each of these methods and some help deciding which way is best for you:

Method #1: Test a Power Supply Manually with a Multimeter

See How to Test a Power Supply Manually with a Multimeter for a full tutorial.

Advantages of a manual PSU test:

  • The only tools needed are a screwdriver and a multimeter, both of which you likely already have. If you don't own a multimeter, you can usually find a basic one at any major retailer for around $20 USD or you can find one online if you don't mind waiting a few days.
     
  • Assuming you have a multimeter and screwdriver, you can test your power supply right now following the directions above.

Disadvantages of a manual PSU test:

  • It's manual! It is going to take a little work on your part to thoroughly test your power supply.
     
  • Testing a PSU manually can be dangerous if you're not very, very careful. See my warning at the bottom of the page for more information.

Method #2: Test a Power Supply Using a Power Supply Tester

See How to Test a Power Supply Using a Power Supply Tester for a full tutorial.

Note: The instructions linked to above are specific to the Coolmax PS-228 ATX Power Supply Tester but the general idea applies to nearly any tester you choose to purchase.

Advantages of using a power supply tester:

  • It's automatic! Power supply testers were invented because manual tests are manual and introduce human error. The results of a PSU test with a power supply tester unit is more conclusive.
     
  • Testing a power supply with a power supply tester is a safer than testing one manually. A power supply tester lets you stay a bit more removed from the electricity than with a multimeter test.
     

Disadvantages of using a power supply tester:

  • Chances are you don't have a power supply tester so you'll have to buy one. Depending on your choice of tester, you're probably looking to spend from around $10 to $40 USD. Here's a list of PSU testers at TigerDirect.
     
  • Again, you probably don't have a power supply tester, meaning that you'll have to order one and wait until it shows up before you'll be able to test your power supply. That could mean that you live with a major computer problem longer than you'd like.

Extremely Important: Take great, great care when testing a power supply, especially if you've chosen to test it manually. Both methods above involve working with a high voltage power supply while it's plugged in. If you're not extremely careful you could electrocute yourself and/or damage your computer. I don't mention this to frighten you - testing a power supply is a common troubleshooting step and can be done safely if you exercise common sense and follow directions exactly. Just please be careful when doing so.

Did your power supply fail a test?

Replace the power supply. That's right, just replace it, even if it's partially working.

It is never a safe idea to fix one yourself. If you insist on having your PSU repaired rather than replaced then please seek the assistance of a professional repair person.

DO NOT open a power supply's cover under any circumstances! The image on this page is for illustration purposes only, not as a direct example of testing a PSU!

Having Problems Testing a Power Supply?

See Get More Help for information about contacting me on social networks or via email, posting on tech support forums, and more. Let me know what kinds of problems you're having testing your power supply and I'll try to help out.

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