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The Most Random Shut Downs, You Gotta Hear This!

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Computer Specs:
CPU: Intel Core 2 6600 @ 2.4ghz
Graphics Card: BFB NVIDIA 8800GTS
Motherboard: ASUS P5B
Memory: 2GB Patriot PC2 6400 RAM
Power Supply: Aero Cool 650W
Hard Drive: 320GB Seagate
Thermaltake Cooling System
Operating System: Windows 7 Ultimate

Here is my problem:

The computer is very fast(could be faster with better RAM!!), has 5 or 6 fans buzzing around in there and the graphics card is great. It runs most every game out there and can handle Adobe CS4 without even missing a step. However, when I am off of the computer for a few hours, and itís on, it will just randomly shut off.

My first thought was that it was too hot, but I check the temperature inside the tower in system setup and itís mid-40ís and I honestly have an amazing cooling system. So I doubt it shuts off because it gets too hot. Then I went and looked at the tower and on the mother board there is a bright green light that is on!? So I have to flip the switch on the power supply and then 3-5 seconds later the light on the mother board shuts off. Then I turn the power supply back on and then turn the computer on and it fires right back up again, no problems at all?!

I just donít know what this could be?? What would cause the computer to shut off, but the motherboard is still on until I turn the power supply off? Is it the graphics card? Does RAM have anything to do with it? I am so clueless and canít afford to go pay a repair shop $70/hr to diagnose it! Any help will be greatly appreciated!!! Thank you.
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Install PC Wizard (lets check fans and temps):
  • Click PC Wizard in my signature
  • Click PC Wizard 2010.1.93 on the top left
  • Save the file to your Desktop
  • Double Click the setup file
  • Follow installation instructions
  • Once installed, open PC Wizard up
  • Click "Tools"
  • Select "Options"
  • On the "View" tab, tick "sensors in real time"
  • On the "Monitoring" tab, tick "force fan detection"
  • Click OK
  • Click the Posted Image icon
  • Click the refresh Posted Image icon
What do the temperatures say? What do the fan speeds say? What about power supply voltages? Posting a screen shot is best, or post the information in your next reply.

Posted Image

Lets double up on the temp. checking...
  • Download CoreTemp
  • Select whichever your OS is, 32bit or 64bit (if you don't know, select 32)
  • Open with Windows Explorer
  • Click Extract Files (save to a location you can remember)
  • Double Click Posted Image
  • Post ALL information or post a screenshot
Posted Image

Does the computer blue screen or just completely shut off?

If it just randomly shuts off, see if chkdsk helps.

Try running chkdsk /r
  • Click Start (in Vista or in 7, Windows Orb)
  • Click on Run...
  • Type or copy and paste chkdsk /r
  • Notice the space between the k and /
  • Click OK
  • You will be prompted that it cannot run, and
    asked if you'd like it to run at startup, Enter
    Y for Yes
  • Press Enter
  • Restart Your Computer
Chkdsk will run, the percentage of completion will even appear to go backwards at times and this process make take several hours to a couple days to complete. Once it has finished, your computer will restart.

Please report temperatures/screen shots and include the voltages of the power supply. Does the computer randomly shutting off anymore after chkdsk.

Edited by Ferrari, 20 March 2010 - 08:29 AM.

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Follow what Ferrari is suggesting.

To answer this question.

What would cause the computer to shut off, but the motherboard is still on until I turn the power supply off?

The light is 5vdc standby power and will always be there if the PSU is on and putting out the 5vdc.
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    Grumpy Ol' MSgt (Ret.)

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The light is 5vdc standby power and will always be there if the PSU is on and putting out the 5vdc.

To clarify just a bit, that standby voltage will always be there if the power supply is plugged in, and IF equipped, the master switch on the back of the supply is set to on. If, like many, your PSU does not have a master power switch, then that standby voltage is always there when the PSU is simply plugged in to the wall. It is this standby voltage that, among other things, signals the PSU to start when you press the front panel power button to start your computer.

That LED you see is really a warning - telling you there is power present and to unplug before reaching in to clean, or to add or remove hardware, especially RAM.

Sudden shutdowns and reboots can be caused by many things - but certainly heat must be ruled out quickly. So I agree with Farrari's approach. Do note that effective cooling is achieved by good air flow and not by the number of fans in the case. You want a decent flow from front to back through the case. Fans blowing in from all directions can cause turbulence and disrupt flow. Make sure your fan are blowing the right way.

Also, multiple intake fans means more heat trapping dust is sucked in too.

Other causes of sudden reboots are malware, leaky capacitors, failing or stressed power supply, failing RAM, failing motherboard. Have you scanned for malware? Inspect your motherboard for bulging or leaky capacitors (they look like tall soda cans). You can test RAM using one of the following programs. Both require you to create and boot to a bootable floppy disk or CD to run the diagnostics. Allow the diagnostics to run for several passes or even overnight. You should have no reported errors.

Windows Memory Diagnostic - see the easy to follow instructions under Quick Start Information.
MemTest86+ (for more advanced users) - an excellent how-to guide is available here.

Alternatively, you could install a single RAM module and try running with that to see if it fails. Repeat process with remaining modules, hopefully identifying the bad stick through a process of elimination.
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