I'm helping a friend troubleshoot a desktop PC that stopped working after a power interruption. While he was away, someone unplugged the extension cord powering the PC, monitor, and other equipment. When he returned, the USB keyboard was not detected, and the computer displayed a warning about insufficient power. After reconnecting the setup to the same outlet, the main breaker tripped and the entire house lost power. Resetting the breaker and trying that outlet again caused it to trip a second time. The equipment was then moved to another outlet: the lamps and monitor work, but the PC itself shows no signs of powering on. The system had worked reliably for roughly four years. Could the power supply have failed, or might the extension cord or outlet have caused additional damage? Are there any safe checks to perform before taking the computer to a repair shop?
4 Answers
Check the simple things first: make sure the PSU’s rear switch is on, the power cable is fully seated, and the motherboard’s 24-pin and CPU power connectors are firmly attached. Some power supplies also have protection circuitry that needs a full discharge—unplug it, switch it off, hold the case power button for several seconds, then reconnect it once. Don’t do this with the outlet that repeatedly trips.
The power supply is the most likely failure point, especially since the breaker trips when the setup is connected. Disconnect the PC completely and don’t keep testing the suspicious outlet or extension cord. If you have a known-good, compatible PSU, testing with that is safer than repeatedly resetting the breaker. A UPS with surge protection is also a good idea for the replacement setup.
A PSU paperclip test can indicate whether the power supply starts, but it’s not a complete test and should only be done if you’re comfortable following the PSU manufacturer’s instructions exactly. Unplug all components first, use the correct pins, and never open the PSU casing. A shorted graphics card or another component could also be causing the PSU to shut down.
Because the main breaker trips rather than just the PC failing to start, the outlet, extension cord, or household wiring may have a fault in addition to a possibly damaged PSU. Stop using that outlet and cord, and have an electrician inspect them. If a replacement PSU also trips the breaker, don’t continue troubleshooting the computer yourself.
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