Windows 7 PC shuts itself off

Hi Guys,

Whats the best way to test a power supply? Is it possible for a power supply on the blink to work for 15-45min bursts then turn itself off?

Anything else that might cause random shut downs? No blue screen PC just turns off like power has been lost.


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Try to disable automatic reboot at systemfailure.

Right click och Computer -> Properties -> Advanced system settings -> Startup and recovery -> Uncheck the "Automatically restart" option
Randy DownsOWNERCommented:
power supplies usually die and don't ever turn on again. I suspect you have an over heating problem. Check CPU & video fans.
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Dear Matt,

it may also be that your Windows 7 license is not currently activated - that may cause it to shutdown.
You can see that in Control Panel > All Control Panel Items > System (or simply "Properties" of your computer).

Kind regards,

Sounds most like a thermal event to me - either the processor or the PSU itself.

Job 1 - a REALLY good blow through with an airline (preferably) or an air duster.

Job 2 - clean the proc/heatsink interface and reapply a GOOD thermal paste (artic silver or similar).

If you want to try monitoring the proc temp,
Speedfan ( is a reasonable free program to try, and it may point the direction - but tbh the best bet is to make sure there aint a problem to start with by doing the above jobs first!

Clean the contacts on the memory sticks and any attached cards (video etc) with your preferred cleaner (eraser/spirit/sandpaper (joking)) and make sure everything is well seated.

I assume no errors in the system log?

If all else fails, the obvious thing is to try a new PSU on a soak test. Only start worrying if THAT fails.....
I have seen power supplies heat up and go out of spec.
Here's the PSU tester I use -
though I got mine on sale for under $10 w/S&H... but if you need one now, that's not a bad price. Plug in to as many ports on it as you can, turn on the PSU, note the readings, let it run about 20 minutes and note the readings again.

I agree with chrisalis about preventative maintenance on other heat sources, too.
I don't know how old you are... I bought a tube of Dow 340 Heat Sink Compound about 20 years ago, have done dozens and dozens of heat sinks with it, and it's only about half gone.

Reseating RAM sticks is about as far as I'd go on those... the gold plating won't stand up to much cleaning, and once that's gone the only thing you (without massive expenditures) can do for them is silver plate, which still allows more oxidation than the stock gold plating (but is 40x less resistive than copper oxidation).
Mea culpa.

I'm obviously going to have to be a little more careful about whose leg I pull on here!- I tend to forget sometimes I'm not just dealing with fellow Liverpudlians.

The comment about cleaning contacts was meant just a WEE bit tongue in cheek (hence the "KIDDING"  comment.) In my experience, one of the best things to use on MOBO contacts is a nice soft pencil (NOT INK) eraser which will take any airborne contaminants away and doesnt seem to do any harm to the gold contacts. (I carry one in my toolbox in a dustproof container)

As for heatsink compound - I scrounged mine from a local PC shop about six years ago- I was desperate for a tube and had run out; the guy in there let me have "the end of the tube" as he reckoned it only had about one more install in it.

Ive done countless machines with that tube since then (you only need about half a rice grains worth) - so I reckon he must have been repairing boilers in his spare time with HIS half!

And Just for the record - I do NOT advocate the use of sandpaper, power tools or shot blasting on the memory contacts of motherboards....
SconeComputersAuthor Commented:
Thanks everyone for your responses. I think the issue was a faulty on/off switch on the back of the power supply. Flicking it to the off position the PC turned on and was stable. Bizarre.

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Possibly the base unit has been living in its natural habitat - under the desk, and the power switch has been resting against the leg of the desk - HOWEVER..... have a power supply with a switch that is passing mains voltage in the OFF position?

That sounds like a SNAFUED power supply to me - and a fire waiting to happen.

The very least I would do is to either replace (or bypass) the defective switch.
Is the switch flipped toward the O or the I when it works?
SconeComputersAuthor Commented:
O mate.Bizarre eh.
SconeComputersAuthor Commented:
Strange problem.
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