Intermittent unexpected shut down

Hi guys,

This is my first post.

I've had something strange happen twice to my PC in the last few weeks, and I am having trouble tracking down the cause of the issue.

First time it happened, I was using the PC normally, with everything working as you would expect, when suddenly, without any warning, the PC stops dead - all I am left with is a flashing green power light. The PC will not reboot, until I kill the power supply for 10-15 seconds, when it will reboot as if nothing has happened and work normally again.

I've taken the sides off and looked for any obvious loose wires, as well as blowing out the dust. But found nothing of note.

Motherboard / CPU / RAM all about 4 months old. Graphics card about 12 months old.

I run a temp monitor - Case +/- 34*C, CPU temp +/- 42*C GPU temp +/- 42*C, HD 36*C (all temps approximate within 1 or 2 *C) so I am discounting overheating.

Last night I installed, updated and played Portal for nearly 4 hours or so, closed the game down and was doing some general PC filing for around 20 mins, when it stopped dead again - flashing green power light. I shut off the switch to the power socket for 10 secs, and bingo, everything back to normal again.
When the power light is flashing, there are no POST beeps, and the power buttons / reset button are useless.

The power leads are all plugged into a multi-plug surge protector, and there is no lightning etc.

I've had a search on the internet and found very little that helps.
I did find that the symptoms are similar to Hibernate mode - but I've checked and that is disabled in the power settings.

Another result mentioned the CMOS battery - could this be causing this very random and intermittent fault.

Lastly, I considered it may be something to do with the power supply, but I wonder if the power supply was at fault, would it not be causing a shut down more often ?
I'm going to swap out the power lead later in case there is a short there, but have I forgotten to check something ?

Strangely, just happened again.
Been playing games for 2 or 3 hours, no problems. Finished playing, GFX card and CPU cooled down (from mid 50s to upper 30s Celcius), was surfing the internet for an hour, no problems. I went to make a coffee - PC had shut down by the time I had come back...

What I can't work out, is why it shuts down when NOT under load.

Any and all ideas welcome - thanks !

System - Athlon 64 X2 5200+ 2GB DDR2 800 Geforce 7600GS AGP

 

Well over heating would always be the first thing I would look at. Secondly I'd check the outputs from the PSU just in case one of the levels is a bit too low. And I'd also check the RAM using something like Memtest.

Welcome to MG by the way.

 

Thanks Yargwel, I have completely ruled out over heating - my system very stable at 55*C + for both CPU and GPU, with case and Hard drive temps in upper 30s *C
I did take out the AGP card and cleaned the fan assembly and re-seated it with new thermal paste. I also made sure all cables / Ram attached securely.
So far, no unexpected shut downs since I reinstalled it.

I'm considering that it may have been a slightly loose AGP card (the MSI mobo doesn't have a locking clip)

 

That's good. What I really meant about the RAM was occasionally you can get a bad memory address. Memtest will check that out. One of my PC's had started to act strangely on occasion and it turned out to be a failing RAM stick so it's always worth just checking. And if you find no problems then that's one more thing to eliminate from your possible causes pile.

 

Okay, I had it shut down on me again tonight.

I've checked the event viewer which was showing some Hard Drive read / write errors, so I fixed those to eliminate them. I think these were paging file errors too. Funny that event viewer doesn't record anything in the time immediately before shut down.

I also found, that the "Spread Spectrum" was enabled in the BIOS , despite previously setting it to Disabled. This may have a possible impact on the issue - I've no idea how it got changed, but I've disabled it again "for system stability" - I've never had EMI issues.... so why have it enabled ?

AMD "Cool n Quiet" was set to Auto - should I disable this as well ?

I also tracked down an IRQ conflict between my Graphics card and my USB expansion board, which I've sorted out as well.

I'll run Memtest when I have some spare time

 

Yargwel, I did the Memtest (only one pass due to time constraints) with no errors found.
Curiously, Memtest detected my memory as 450Mhz (DDR900) when it is clearly set in the BIOS as 400Mhz (DDR800) and DDR800 is shown on screen during the boot sequence....

 

I bet would be dodgy PSU.

 

Can happen.. Sometimes a RAM chip can be made to be a particular speed but if it can't perform the correct number of operations that manufacturer's testing specifies it will get rated and sold as a lower speed chip. I wouldn't worry about it.

Have you had chance to check the output voltgaes of your power supply yet?

 

I watched the voltages in the BIOS for around 5 minutes, and the ratings are as follows - (I don't have a volt meter to check manually)

VCORE fluctuates between 1.26 & 1.33 V
+12V fluctuates between 11.98 & 12.14 V
+3.3V fluctuates between 3.24 & 3.3 V
+5V fluctuates between 5.06 & 5.59 V
VBAT fluctuates between 3.15 & 3.16 V
5VSB fluctuates between 4.99 & 5.01 V

Memory Voltage 1.9

These rates are virtually identical to those shown using 'Everest' system analyser.

Everest also has an entry called +5V Standby which is steady at 4.95V

The computer hasn't shut down today and I've been playing Half-Life2 for most of the afternoon. The PC 'feels' a bit more responsive since turning off the Spread Spectrum in the BIOS - Is it worth getting voltage readings with Spread Spectrum turned on ?

Many thanks, btw

 

Well those voltage levels are fine. I'd personally just leave the Spread Spectrum turned off but maybe for interests sake you could see if it is affecting the voltages but I'll leave that up to you. . I'd just see if the PC runs OK for a few days without it turned on - if it does then it's probably your culprit.

 

Well, no unusual shut down since I turned the Spread Spectrum off - I think I'll just leave it as it is now.

Many thanks for your assistance Yargwel !