My computer would not power on this morning. I noticed that the voltage regulator had shut itself off, so I disconnected the PC, restarted the regulator, and connected the computer again, but it still showed no signs of powering on. The regulator now indicates that the wall voltage is too high. My power supply is rated for input up to 240 V, but I do not know the actual voltage being supplied. Do modern PSUs shut down when they detect excessive voltage, and is it safe to try again once the voltage returns to normal? If the computer remains dead, how can I determine whether the PSU or the motherboard failed?
2 Answers
Do not keep trying to power the PC while the regulator is reporting high input voltage. Many modern PSUs accept a broad range, commonly around 100–240 V, but that does not mean they can safely handle voltage above their rated maximum. Wait until the utility voltage is confirmed normal, then try a different known-good outlet or power cable if appropriate. If there is still no response at all, the PSU is the first component to test or replace, ideally with a known-good unit. A PSU tester can help, although testing with a known-good PSU is more reliable for diagnosing the motherboard.
A PSU may shut down because of an over-voltage or surge-protection event, but simply holding the power button for a few seconds is not guaranteed to reset damage or a failed unit. Unplug the computer completely and leave it disconnected until the incoming voltage is normal. Once it is safe, check that the PSU switch, power cable, and regulator are working, then try powering on once. If there are no fans, lights, or other signs of life, test with another compatible PSU before concluding that the motherboard needs replacement.
I waited for the voltage to return to normal, but the computer still did not turn on.
The regulator only tells me that the wall voltage is high; I do not know the exact reading. There was a thunderstorm and unusually high voltage across the area, so I will wait until it returns to normal before testing the PC again.