[clug-talk] OT: Computer Power Issues

Dave Bourassa dave.bourassa at shaw.ca
Fri Jan 28 18:53:39 PST 2005

Peter Carless wrote:

> Hi Jason,
> This may be a long shot but have you checked to see if the voltage 
> selector switch on the power supply is set for 115v and not 220 volt.
> I once put together a machine with a brand new case and power supply. 
> The computer booted up, but acted really flakey, after trying quite a 
> few things to no avail I discovered that the power supply was set for 
> 220 volts. Switching to 115 volts cured all the problems.
> Before this experience I would have assumed that the power supply would 
> not work at all if the switch was set to the incorrect voltage, but 
> apparently this is not the case.
> I admit that this is a very long shot, but it will only take a few 
> seconds to check. The voltage selector switch is usually located on the 
> back of the power supply and you should not even have to crack the 
> computer case to check it
> Peter

snipped a bunch ...

Hi Jason,

Your 117v reading is entirely normal.  You could probably drop it down 
to less than 90 volts before you'd have any problems.  The power supply 
in your pc is a "switching" voltage regulator design using toroidal 
transformers.  They'll take the ac voltage coming in, change it to a 
very high voltage/very high frequency and then back down to plus/minus
twelve and five volts dc.  The dc levels are rock solid and there is a
large variance in the ac voltage allowable.  Any deviation from the
nominal allowed voltages will result in the ps shutting itself off.

There still could be problems with the power supply in that it is not
working proberly due to requlating circuitry malfunctions, etc.  Other 
problems are hair line fractures on the mobo., bad or flaky memory 
chips.  Try removing all your socketed cards, including memory, cleaning 
the contacts and replacing them in the SAME sockets.  If that doesn't 
clear up the problem, trying a 350watt (or 400) would be worth a try.

                     Dave Bourassa at
                 mailto:djb at calpc.org
      "There are 10 kinds of people in the world. Those who
           understand binary and those who don't."

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