A computer setup had been working normally for about four years. While the owner was away, someone unplugged the extension cord powering the PC, monitor, and peripherals. After everything was plugged back in, the USB keyboard was not detected and the computer reported a power-related error. Unplugging and reconnecting the setup then immediately tripped the main breaker and cut power to the house. Resetting the breaker and trying the same outlet caused it to trip again. The equipment was moved to another outlet: the lamps and monitor work, but the PC itself will not start at all. Could the power supply have failed, or might the extension cord or outlet have caused the problem? What checks are safe to perform before taking the computer to a repair shop?
3 Answers
The power supply is a strong possibility, but don’t assume it’s the only issue. Repeatedly tripping the main breaker points to a short or other electrical fault, so stop using that outlet and extension cord for now. Don’t keep testing the PC there, and have an electrician check the outlet and circuit. If the PC is tested, use a known-good outlet and a properly rated power cable, with all peripherals disconnected.
Since the monitor and lamps work from the other outlet but the PC remains completely dead, the computer likely suffered a PSU failure or damage to another internal component. The original outlet or extension cord may also be defective, especially because it repeatedly tripped the breaker. Have the electrical side inspected before plugging the computer back into that circuit, then have the PSU and motherboard tested.
A PSU can fail in a way that causes the breaker to trip, and a faulty graphics card or another component could also be shorting. The safest basic checks are to verify the PSU’s rear switch is on, try a different power cable, and disconnect USB devices and internal add-in hardware if you know how to work inside the case. Avoid opening the PSU itself. A paperclip test can be dangerous and only checks whether the PSU starts, not whether it is safe or working correctly, so swapping in a known-good PSU or having a shop test it is preferable.
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