[Gllug] Computer won't turn on

Chris Bell chrisbell at chrisbell.org.uk
Fri Dec 3 10:58:22 UTC 2010

On Fri 03 Dec, Sanatan Rai wrote:

>      The CPU fan does start---briefly---and then the system cuts
> out again. So what happens is the following:
>    1 PSU switch at the back is on
>    2 Press on button at the front of the computer: nothing happens
>    3 Toggle PSU switch on--> off --> on
>    4 Press on button at the front of the computer, fans start spinning,
>       I see the light under the front button turn on, then the system
>       powers down in seconds. The CPU fan does not reach full
>       speed---I think all this happens in under 5 seconds.
>    5 We're back in state 1
   I have seen PSU shorted by a damaged USB connector, (attempts to power up
but then fails safe), but on a laptop the more usual fault is a damaged
   Most ATX PSUs can be disconnected from the computer then tested by
measuring the standby +5 volts off load, which is also used to power the
main "start" lead (usually close to +5 volts). Use a piece of wire to short
the "start" lead to 0 volts and the main power should appear on all leads
and be close to the correct nominal voltages. To be safe I use a mains
isolating transformer fed through a dummy load such as a mains voltage
tungsten lamp so that I do not trip the breaker with a faulty unit.

Chris Bell www.chrisbell.org.uk (was www.overview.demon.co.uk)
Microsoft sells you Windows ... Linux gives you the whole house.

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