How Do You Troubleshoot A Power Supply Unit

The all too common question, "how do you troubleshoot a power supply unit?" typically follows abrupt power failure on a computer. Chances are you shut down your computer and you went to turn it back on, only to find it won't power up. It is necessary to troubleshoot a power supply unit to determine if the power supply is the true cause of the problem, how to repair it and how to restore your computer back to a functioning state. Common signs of problems with a power supply unit include problems powering on, random restarting, shocks produced by touching the case, smoke and popping noises when the computer is powered on.

  1. Cycle all power. Troubleshooting should start with the most obvious step, power down the computer. Disconnect the power from the power supply unit and leave it disconnected for at least ten minutes. Plug the power supply back in and attempt to power on the computer. If the computer is still experiencing issues continue to the next step to troubleshoot a power supply unit.
  2. Test the output voltages. Troubleshoot using a digital multimeter and a technique called back-probing, you will need to test the output voltages of the power supply unit. Obtaining a proper reading will require the power supply unit to be connected to the computer as normal, under normal strain. If you are unfamiliar with back-probing or how to use a digital multimeter, it will difficult to test a power supply unit.
  3. Try a different unit. Swap the power supply unit for a different power supply unit and power on the computer. Check to see if the problem persists. If the problem does not exist when the other power supply unit is plugged in than this guarantees the problem is in-fact the power supply unit. If the problem still persists this more than likely rules out the power supply unit as the source of the problem.
  4. Replace the unit. If the power supply unit is proven to be the problem, immediately replace the unit. Troubleshooting will not fix it. Using a computer with a malfunctioning power supply unit can lead to more damaged components and worsen the problem far beyond the power supply unit. 


  • If the computer completely fails to power on, the power supply unit is the likely cause.
  • If the computer briefly powers on and then immediately off, the power supply unit is a likely cause.
  • If there is smoke, burning smell or popping sounds immediately turn off the computer. Carefully examine the power supply unit as it is the likely cause.
  • A power supply unit can become damaged over time or as a result of an electrical surge or outage.
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