We have a rather old computer in our office that my parents use. Every time there is a power outage in the house, the computer is a little difficult to power back on. When pressing the power button, the PC will remain on for 3 or 4 seconds, power off, and then you'll hear one last "breath" from the PC before powering off for good.
I have generally resolved this by unplugged the power cord from the PC, reconnecting the power cable from the PSU to the motherboard, holding down the power switch (with no power cord attached) to drain any voltage within the computer (is that true?). Usually it powers on afterwards.
But sometimes, and this has happened several times, when reconnecting, the PC will immediately power off after re-connecting the Ethernet cable, which I find really strange.
This is a 650V PSU. Is the thing just going bad? Is it somehow not getting enough power to prop up everything within the PC? Or does it sound like something worse?