Make, model OS etc.
Dafydd.
My computer will not boot up at all when restart is selected, or when trying to restart after updates are installed, it will just sit there and never boot up, with the monitor black. I have to shut it down, then turn it back on and hope it boots up after about 15 minutes, if not, I unplug it, leave it unplugged for 15 minutes, plug it back in but not press the power button for another 15 minutes, then press the power button and hope it boots up within 15 minutes after that, if not, rinse and repeat. The light on the power button comes on right away, so I know it's getting adequate power. I took my computer to a repair shop and explained this problem, I was told I had a bad power supply, and a new power supply was installed. The guy tuned it on in the shop, and it booted up within a few seconds as it should, but as soon as I got it home, I had the same problem. The computer doesn't show any signs of lacking power when running, it doesn't flicker or anything.

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