> > >
> > >Say PC user want to clean power supply internally, decides to do it the next morning, so the PC not used for a night. (Power supply is not turned off, and stays plugged into wall socket which is powered).
> > >
> > >Would the PC power supply still contain a high/dangerous charge or would it be low charge/power/risk ? :)
> > >
> > >Bye,
> > > Skybuck.
> > The PFC boost cap can run around 400 volts. I'd expect it to discharge
> > in a few minutes after the box is unplugged, but you could check it
> > with a voltmeter.
> >
> > The 400v is there even if the PC is "turned off" because the supply is
> > still making standby voltages. It's not really off unless you unplug
> > it or flip a real switch in the back.
> >
> > The stored energy could surprise you but is unlikely to be lethal. > >
> > Why not unplug it overnight? Or clean it without pawing things. >
> Highly unlikely - these circuits are designed for efficiency, not energy storage.
The mains delivers power at 50Hz in the Netherlands, where Skybuck lives, and 60Hz in the US. The power supply has to store enough energy to deliver constant power over that period - power factor correction means that the current extracted from the grid has to be more or less sinusoidal, so no matter how efficient it is it does have to store an appreciable amount of energy, almost always in a capacitor. They tend not to discharge all that fast after the power supply is unplugged.
If Gnatguy knew anything about practical electronics he'd be aware of this. He'd have found it out the hard way.