Intermittent powering-up problem.

  Mr Mistoffelees 09:44 31 Jul 2005
Locked

When I shut my pc down for a long period, such as overnight, I always turn off the power at the wall socket. Recently, on some occasions, when I try to boot-up again the pc starts to power-up but before the fans are up to speed, less than a second typically, it will go off again. I then have to switch the power off at the wall and then on again before the pc will again respond to the power button, at which point it will always run faultlessly. I think this is either a fault or a quirk of the psu, which is only a few months old and more than adequate for the task. Does anyone have any ideas?

  Mr Mistoffelees 10:45 31 Jul 2005

^^^^^^^^^^

  Fruit Bat /\0/\ 11:27 31 Jul 2005

Modern PCs have power trickling into the motherboard via the PSU even when the front power switch is off.

The power switch is just a signal to the board not a true isolating switch.

To put it simply, when you switch off at the socket you kill the feed to the psu and capacitors discharge. The recharging of the capacitors causes power drop and the effect you have describe.

  Mr Mistoffelees 13:45 31 Jul 2005

I thought that might be the case. What concerned me was that this has only happened recently so I will see how it goes for a while. It seems clear that all it should need is a few extra seconds delay to allow capacitors to recharge.

  Mr Mistoffelees 19:49 09 Aug 2005

Over the last few weeks there have also been other problems which, combined with the above, suggested the psu was not regulating it's voltages very well and, in the last few days, were getting worse. Asus PC Probe showed they were a little out too. At the weekend I fitted another new psu and PC Probe showed that the 3.3V and 5V rails were nearer the correct values. So far since then there have been no problems.

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