Replacing a Power Supply for Your PC: Diagnostics & Installation

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A step-by-step guide to testing and replacing a PSU
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When a PC power supply dies or begins to wear out, it must be replaced. With a few simple tools and the help of this guide, you can do this job yourself and save on expensive repair fees.

How can I tell if my power supply is failing?

A failing PSU may cause power failure, blue screens of death, freezes, or trouble running power-intensive programs. In extreme cases, you may smell burning or see smoke. If you do, shut the power supply off immediately. It’s unsafe to use.

Section 1 of 3:

Signs of a Failing PSU

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  1. 1
    No PC Power The power supply’s primary job is to provide power to all of the components in your PC. If your PSU is bad, though, it may not provide enough juice to power on the PC. If you’ve confirmed everything is plugged in correctly and you still aren’t getting power, the PSU is the most likely candidate for the problem. [1]
  2. 2
    Random blue screen errors Blue screens of death (BSoD) can be triggered by a variety of issues, but a power supply that’s providing uneven power will cause a PC to run into all kinds of errors. BSoDs are your PC’s way of going “something is seriously wrong, so we’re shutting the PC down to prevent something really bad from happening,” and a failing PSU will cause that to happen a lot. [2]
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  3. 3
    Frequent freezing If there isn’t enough juice going to your motherboard or CPU, the computer will freeze up. If you’re also seeing frequent freezes that require restarts, it could be a sign of a bad PSU. [3]
  4. 4
    Trouble running power-intensive programs This is a major sign your PSU or GPU is bad. If you try to run recording software, video editing software, or a video game with really good graphics and the computer stutters or freezes, it’s a major sign that something is wrong. [4]
    • If your PC crashes or BSoDs when doing this, it points more toward the power supply. If you have zero problem closing the program and then the PC goes back to normal, it’s more likely to be the GPU.
  5. 5
    Overheating After your PC has been running for a few minutes, put your hand on the outside of the case where your PSU is located. If you feel it getting very hot, it’s a sign your PSU is going bad. The PSU should only get a little hot under heavy loads, and the fan on the PSU should keep things from getting too out of hand. [5]
  6. 6
    Strange noises Your PSU should basically never make noise. If you hear clicking, whining, or odd noises of any kind coming from the area near your PSU bay, your power supply is almost positively bad. [6]
  7. 7
    Burning smells or smoke If you smell burning and your GPU isn’t actively on fire where the supply cables feed into it, it’s your PSU. Any kind of smoke is also confirmation your power supply is bad. The other components in your PC just aren’t realistically capable of catching fire the way PSUs can. [7]
    • Shut your PC off and do not turn it back on if you smell burning or see smoke. PSU fires can get out of hand very fast if they’re allowed to burn for long.
  8. 8
    No fan spinning Check out your PSU when the computer is running for a while. Is the fan spinning? If it isn’t, try turning on a power-intensive program. Does the fan turn on? If it doesn’t, your PSU is probably bad. [8]
    • The PSU fan shouldn’t always be on. Under low loads, the fan stays off because there’s no need to pull in cooler air. On heavy loads, though, the fan should always be on.
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Section 2 of 3:

Testing a PSU

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  1. 1
    Set up your multimeter using the DC voltage position. The black negative lead must go into the COM jack on your multimeter, and the red positive lead must go into the VΩmA/μA jack. Then, turn the dial to the V with a solid line on top and a dotted line underneath. This is the DC voltage position.
    • When to test a PSU: You can normally tell if a PSU is bad just by deductive reasoning, and this is not a test most PC builders should need to do. However, you may want to test your PSU this way if you really can’t figure out if the PSU is the culprit for your PC woes, or if you have some signs of a bad PSU but not very many of them.
  2. 2
    Trick your PSU into turning on with a paper clip. Unplug the PSU and set the power switch to off. Put on some electrician’s gloves and grab a paperclip. Undo the paper clip and shape it into a U. Grab the 24-pin ATX connector and orient it so that you’re looking at it vertically with the security clip that locks the cable onto the motherboard on the right side. If your pin is color-coded, connect the green to any black. The green is your power on the port, and the blacks are grounds. Insert the tip of a paperclip into the green port and the other into any back.
    • If your pin isn’t color-coded, connect port 16 to port 19. With the cable vertical, 1 is on the top left, and the numbers go down to 12. On the top of the right-hand column, it starts at 13. Count down to 16 and insert one end of the paperclip. Then, count down to 19 and connect the other end.
  3. 3
    Plug the PSU in and flip the power switch on. The paperclip is going to trick your PSU into thinking it’s feeding power to a motherboard. Don’t touch the paperclip while you work. It’s unlikely that you’ll shock yourself enough to hurt anything, but it isn’t worth risking it.
  4. 4
    Connect the black lead to any COM port on your connector. This will ground the multimeter so you can get an accurate reading as you test the remainder of the ports. If your cable has no labels, use port 7, which is directly across from the grounded end of the paperclip but in the left-hand column.
  5. 5
    Test each port to see if the cable is getting proper power. With the black port inserted, plug the red probe into each remaining port and take a reading. The ports should give different values depending on which port you’re testing, and we’ll list the expected values below, but if you get any whacky or illogical readings (or a port is just dead), your PSU is bad. The generally expected ranges are (skipped ports are grounds and should give no reading):
    • Pin 1: +3.135 to +3.465V
    • Pin 2: +3.135 to +3.465V
    • Pin 3: +4.75 to +5.25V
    • Pin 4: +4.75 to +5.25V
    • Pin 5: +4.75 to +5.25V
    • Pin 6: +11.40 to +12.60V
    • Pin 9: +4.75 to +5.25V
    • Pin 10: +11.40 to +12.60V
    • Pin 11: +11.40 to +12.60V
    • Pin 12: +3.135 to +3.465V
    • Pin 13: +3.135 to +3.465V
    • Pin 14: -10.80 to -13.20V
    • Pin 21: +4.75 to +5.25V
    • Pin 22: +4.75 to +5.25V
    • Pin 23: +4.75 to +5.25V
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Section 3 of 3:

Replacing Your PSU

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  1. You cannot use any PSU for your PC. You must make sure that it has the proper cable connections and slots for your specific build, and the PSU must have enough wattage to power all of your PC components (with a little bit of juice left over). [9]
    • You can use PC Part Picker to test whether your PSU will be compatible and have enough power for your computer, though.
    • Only use the cables that came with your new PSU. PSU cables are not interchangeable, and using your old cables with the new power supply will destroy your computer.
  2. 2
    Ground yourself manually or via a grounding strap. Static electricity can destroy your PC’s components. To prevent accidentally damaging something, keep yourself grounded as you work. Either periodically touch bare metal as you work to discharge any static, or wear a grounding strap while you work. [10] Also, follow these guidelines:
    • Do not replace your PSU while wearing socks. Work barefoot. If you happen to have static dissipative boots, those are fine, too.
    • Work on a wood or concrete surface and avoid carpet. Also, use a wood or natural stone table. Glass is also okay. Nothing fabric, though!
    • Avoid putting a towel down under your PC. As tempting as it can be to try and protect your PC case from accidental scratches, it’s not worth risking your PC’s usability.
  3. 3
    Shut off the power and open your PC case. Shut the PC down and then unplug it. Flip the switch on the old power supply. Then, open your case. On most cases, you have to unscrew two fasteners in the back of the case and remove the top. After that, you simply slide the back panel up to remove it. [11]
    • Every case is different, so if you can’t figure out how to open your case, look up the manual online to find the details.
  4. 4
    Disconnect all of the cables and remove the old PSU. Remove all of the cables where they plug into your motherboard. Then, pull the cables through to the back of the case. Use a screwdriver to undo the fasteners holding the PSU in place and pull the entire PSU out. [12]
  5. 5
    Pre-assemble the PSU by setting up the cables. If you have a modular PSU (which is probably the case), you have a series of cables and ports to attach them to. You’re unlikely to need all of the cables, but there are a few that basically every PC setup will use. Connect the cables you’re going to need now before you install the new PSU, since it’s easier to do it before the PSU is installed. [13] Here are the cables and what they’re typically for:
    • 24-pin ATX: The biggest cable, usually just called a 24-pin, powers your motherboard.
    • 4x4 or 8x8 CPU: You’ll use one or both of these to power your CPU.
    • PCIe (6+2 pin, or 12VHPWR): This is for your GPU.
    • SATA: These are for SATA SSDs, hard drives, optical drives, and fan controllers.
    • Molex: These are kind of outdated now and you probably won’t need to use them, but if you have any older components (like internal screens or WiFi cards), you may need them.
  6. Slide the new PSU into the power supply bank where the old PSU was located, with the cables pointing towards the front of the case. The fan on the PSU must be pointing away from the case. That fan will pull in cold air to cool off your power supply’s components whenever they start to run hot, so the fan cannot be facing your PC’s internals or they’ll just pull in hot air. [14]
    • Screw the PSU into place using the screws that came with your new PSU.
  7. 7
    Run and connect your cables to the motherboard and GPU. Feed the other ends of your PSU cables through the grommets on the case to reach the components you need to power. [15] Here are the typical connections and their locations:
    • 24-pin ATX: This normally plugs into the side of the motherboard on the right, with the pins inserting vertically.
    • 4x4 or 8x8 CPU: The CPU header is almost always at the top of the motherboard. Refer to your CPU’s model to see if you need to use the 4x4 or 8x8 to power it.
    • PCIe (6+2 pin, or 12VHPWR): This plugs into the front of your graphics card. You may only need to use half of the cable if you’re powering an older or lower-end GPU.
    • SATA: The connections here depend on your setup. Most of the time, you’re just going to use these for storage drives.
  8. 8
    Test your PC before reassembling the case. With everything connected, plug your PSU into the wall outlet and flip the power switch on it. Then, press the power button to confirm that your PC turns on. If everything works, reassemble your case and enjoy your updated computer!
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  • Question
    When I turn on my computer it shuts down after about two minutes. It doesn't even boot up to Windows. What should I do?
    Adrian
    Top Answerer
    It is probably a BIOS error. When it is starting up, read the BIOS screen, it may be telling you there is an error and shuts down because it cannot boot.
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  • Question
    Where is the motherboard?
    Community Answer
    The computer motherboard is the large flat piece, usually in the middle of your computer. If you do not know what a motherboard is, you should probably not be fixing your computer yourself.
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  • Question
    What can I do if my power supply cord is damaged?
    Community Answer
    Buy a new cord to replace the damaged cord.
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      Warnings

      • Do not use a power supply if you smell any burning, it sparks, or you suspect it’s going to light on fire.
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      References

      1. ↑ https://gamemaxpc.com/pc-power-supply/5714.html
      2. ↑ https://gamemaxpc.com/pc-power-supply/5714.html
      3. ↑ https://gamemaxpc.com/pc-power-supply/5714.html
      4. ↑ https://eezit.ca/how-to-tell-if-your-power-supply-is-failing/
      5. ↑ https://www.bravoelectro.com/blog/post/power-supply-overheating
      6. ↑ https://gamemaxpc.com/pc-power-supply/5714.html
      7. ↑ https://eezit.ca/how-to-tell-if-your-power-supply-is-failing/
      8. ↑ https://eezit.ca/how-to-tell-if-your-power-supply-is-failing/
      9. ↑ https://www.thegamer.com/psu-gaming-pc-power-supply-beginners-guide/
      1. ↑ https://www.pcworld.com/article/2789275/static-electricity-fried-my-pc-heres-what-i-did-wrong.html
      2. ↑ https://www.thegamer.com/psu-gaming-pc-power-supply-beginners-guide/
      3. ↑ https://www.thegamer.com/psu-gaming-pc-power-supply-beginners-guide/
      4. ↑ https://www.thegamer.com/psu-gaming-pc-power-supply-beginners-guide/
      5. ↑ https://www.thegamer.com/psu-gaming-pc-power-supply-beginners-guide/
      6. ↑ https://www.thegamer.com/psu-gaming-pc-power-supply-beginners-guide/

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