Frequently Asked Questions

  • How do I replace the power supply in my computer?

    If your computer's power supply fails, it cannot be repaired and you'll need to replace it. You may also need to upgrade the power supply to provide more power to your computer for high-end graphic cards.

    Warning: Always disconnect power before opening your computer case and working inside.

    Caution: To avoid damaging components with electrostatic discharge, wear a grounding strap whenever you work on internal components.

    1. Turn off your computer and unplug the power cord from the back of the computer.
    2. Open the computer case, then locate the power supply. The power supply is the metal box that sits at the back of the computer case, usually toward the top, and has several cables coming out of it that connect to other components inside the computer.
    3. Make note of where each of the power supply's cables are connected in your computer case. You can wrap tape around the cables to label them. This will help you connect the new power supply when it's installed.
    4. Disconnect the power supply cables from the components inside your computer case.
    5. Remove the screws that attach the power supply to the case, then remove the power supply. There are usually four screws, and they are unscrewed from the outside of the case at the back.
    6. Place the new power supply in the power supply bay of your computer case.
    7. Secure the power supply to the case with the screws you removed previously.
    8. Refer to the notes you took in Step 3 to connect the power supply cables to the motherboard the same way they had been connected. Make sure the cables are securely connected.
    9. Close your computer case and reconnect power.
    10. Turn on the computer and test the operation of the drives to make sure they are operating correctly.
  • How do I troubleshoot my computer’s power supply problems?

    If your computer turns itself off and on intermittently, won't turn on at all, or has one or more drives that don't work, you may have a problem with the power supply. Try these troubleshooting steps to identify the problem:

    Warning: Always disconnect power before opening your computer case and working inside.

    Caution: To avoid damaging components with electrostatic discharge, wear a grounding strap whenever you work on internal components.

    1. Plug a different electronic device into the power outlet you have the computer connected to. If the new device also experiences problems, the problem is with the outlet's wiring. If the new device works fine, the problem is likely with your computer.
    2. Replace your computer's power cable. If the computer works afterward, the old cable was the problem.
    3. Turn off your computer, then unplug the power cord from the back of the computer.
    4. Open the computer case and visually inspect the power supply for any obvious damage. If it fell out of the power supply bay or has scorch marks on it, it cannot be repaired, and it must be replaced.
    5. Make sure that the power supply's cable to the motherboard is securely connected to the motherboard.
    6. Plug the power cord back into the computer while the case is still open, but do not yet turn on the power switch. Put on a grounding strap, then ground yourself by touching a bare metal surface (other than the computer).
    7. Use a multimeter set to DC voltage to test the power supply. Disconnect one of the cables running from the power supply to any other device, such as a drive, then turn on the computer. Attach the multimeter's red probe to the yellow wire on the power cable, then attach the black probe to the black wire on the power cable. If the multimeter's reading does not equal 12 volts, the power supply must be replaced.
  • How to Check Power Supply Voltage?

    A power supply is an electronic assembly that supplies electrical voltage. If the power supply is part of a larger assembly, such as a computer, then the power supply is meant to provide the voltages necessary to power the rest of the electronics. One of the first steps in troubleshooting a malfunctioning electronic device is to check the voltages from the power supply. If the voltages are correct, the problem lies elsewhere. But if the voltages are not correct, then the power supply can be determined to be faulty or in need of adjustment.

    1. Connect your multimeter probes to your multimeter and turn it on. Observe the correct polarity. The red probe is the positive one, and it is plugged into the red plug on the multimeter. The black probe is the negative or common probe, and is plugged into the black plug on the multimeter.
    2. Set your multimeter function to measure either an alternating current (AC) or direct current (DC) voltage, depending on the output of your power supply. Most power supplies for commercial use produce a DC voltage.
    3. Turn on the power supply. Make sure it is plugged into the appropriate power source. Most power supplies operate by plugging into a typical 120 house circuit.
    4. Connect the multimeter probes to the power supply output terminals by touching the probes to the metal contacts. Power supply outputs are usually marked with a positive (+) sign and a negative (-) sign. Observe the correct polarity with your probes by touching the red probe to the positive terminal and the black probe to the negative terminal.
    5. Read the multimeter display for the output voltage of the power supply.

    Tips & Warnings

    If your power supply voltage is zero, your power supply might have a blown fuse or an open circuit breaker. Some power supply voltages can be extremely dangerous. Make sure you touch the output only with the multimeter probes.