[Gllug] OT: Burnt out power supply

Chris Bell chrisbell at overview.demon.co.uk
Tue Jun 20 23:17:58 UTC 2006

On Tue 20 Jun, Adrian McMenamin wrote:
> A few days ago (when the weather was at its hottest) I noticed my
> computer smelt bad when left off (!), so started unplugging it from the
> mains when the desktop was switch off. Forgot to do that last night and
> woke up to a non-functioning box.
> Took a gamble it was a burnt out power supply and in desperation nipped
> through the empty roads to PC World to buy a new (higher rated) one.
> And, thankfully it worked - making it worth paying the 50% premium.
> But why would it burn out when off? Dodgy transformer? Heat just got the
> better of it?
   ATX power supplies go to "standby" mode but cannot switch off unless
there is a separate mains switch, normally located at the rear of the PSU.
   They continue to provide some standby power, and sit and monitor for the
correct keyboard press, LAN access, etc. This is why you should never plug
or unplug any keyboard, mouse, internal card, or memory card while in
"standby" mode.
   I recently had to junk a motherboard because someone replugged the PS2
mouse with power on. Any mouse attatched appeared to generate a continuous
stream of interrupts and blocked everything else.

Chris Bell

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