# PC failing to boot - Intermittent Problem



## Sarrie (Aug 24, 2011)

Hi all, recently been experiencing some problems with my rig and having exhausted everything I can think of to find the root of the problem I'm looking for anyone that thinks they can shed light on the problem/where to find help. It was built in January this year and has worked perfectly up to this point.

*Symptoms:* My PC is randomly failing to boot, or going black and unresponsive when left alone for a short time. When the PC has successfully booted it seems to rarely go unresponsive until going into sleep mode. The mouse and keyboard also appear to no longer be receving power at this time. It's also gone into this state mid-way through a shutdown.

Perhaps the most intriguing symptom is that holding down the power button on the front of the PC will not turn off the PC when it's in this state, making the only way to power down turning off the switch on the PSU.

When it fails to boot the DRAM LED will normally flash, the CPU fan turns on, the GPU fan turns on, the power lights turn on (essentially it looks and sounds like a normal boot) except nothing appears on the screen. 

The problem occurs seemingly at random and has gone even days without happening and then taken days to boot successfully again. When it boots there aren't any indiciations that I have been able to observe which would indicate a problem wit hteh PC.

*What I've tried:*
Reseating the memory: This worked about 70% of the time when I first encountered the problem but it's effectiveness seems to have reduced dramatically now.

Individually Testing each memory stick: I've found that it tends to crash out on one stick more than the other, but the problem still occurs on both.

Running Memtest86 and The Windows 7 memory checker: Both came up without any problems

Replacing the memory: Tried with an identical stick from my other PC - booted successfully first time but the problem then occurred within 40minutes.

Booting off the MemOK button: Worked the first few times, now appears to be ineffective

Swapping Power Cable: No effect

Re-seating GPU

Removing the Cmos: No effect

Restoring Bios to defaults: No effect

Changing frequency of the RAM (to 1600 mhz) in Bios: Seemed to work for 2 days and then the problem re-occurred.

Removing Everything and rebuilding the PC: worked for 2 days and then problem re-occurred


*Hardware Details:*
Processor: AMD Phenom II X4 955 Black Edition

GPU: XFX HD 6850 Black Edition AMD / ATI Radeon Graphics Card - 1GB 

PSU: 500W Corsair CMPSU-500CXUK Builder Series, 80% Eff', 120mm Fan, Single Rail, ATX

HDD: 2x 1TB Samsung HD103SJ Spinpoint F3, SATA 3Gb/s, 7200rpm, 32MB Cache, 8.9 ms, NCQ, OEM

Motherboard: Asus M4A88TD-M EVO/USB3 AMD 880G AM3 Motherboard

Memory: 2x Corsair Memory XMS3 4GB DDR3 1600 MHz 

Running Windows 7 OS.

I'm completely at a loss as to why it's occurring. My initial thoughts lay with it being a memory issue but the proble has occurred even with RAM from a different PC which is known to be good. The Bios has not be been updated, but I am loathe to do that while the system is currently unstable. 

Any advice would be greatly appreciated. Getting fed up of spending my precious hours in the evening trying to fix it!

I'm leaning more towards a potential power/motherboard issue, although I'm unsure of any concrete way to test these.


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## HARDHELPER (Jul 15, 2011)

Could you try to remove the graphics card and boot it using the onboard VGA just to see if you see something.


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## Sarrie (Aug 24, 2011)

Hi, Just attempted problem still occurred


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## HARDHELPER (Jul 15, 2011)

Do you have a spare PSU just to try?


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## Tyree (May 10, 2009)

The PSU would be suspect. The Builder Series Corsair are OK but not the top quality of the TX-VX HX-AX Series built by SeaSonic and 500W is not sufficient for the 6850 GPU. You should be at 650W minimum.


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## Amd_Man (Jan 27, 2009)

^
As above.


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## Sarrie (Aug 24, 2011)

Hi all thanks for the speedy replies. I have just tested it out with the Spare PSU that I have at home.

The PC booted first time to the Post screen and then quickly cut out again, the second time it booted to ASUS express gate (just before the POST screen) and then cut out, 3rd time it went back to behaving like the other PSU.

The second PSU is also 500w, but surely the test of a 2nd rules out PSU failure? I'm dreading it being a motherboard issue now 

Still intrigued as to why the Power button doesn't turn off the PC when it's held down once the PC crashes out I feel this is a clue somehow ..


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## Tyree (May 10, 2009)

Brand & Model of the 500W PSU you substituted?


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## Sarrie (Aug 24, 2011)

Was an OCZ SXS2 500w 

I'm aware it's not a particularly brilliant brand/model but it's the only thing that I have around the house to test on. It's practically brand new and appeared to be functional. (Based on the fact the PC started up)

The system has functioned for 8months on a 500w PSU so I figured it 'should' work with the OCZ one if it was a power problem.

Still at a complete loss with it


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## HARDHELPER (Jul 15, 2011)

Could you try to boot it without your graphics card with the other PSUs?


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## Sarrie (Aug 24, 2011)

Just gave that a whirl and still no luck, didn't even boot to POST (just usual fans and no response)


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## Tyree (May 10, 2009)

Using an underpowered PSU could have done damage to other components.
Try using the Onboard Graphics and see if the problem persists.


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## Sarrie (Aug 24, 2011)

I attempted using the onboard VGA yesterday as Hardhelper suggested, and had no luck. (and again today with the replacement PSU i tested yesterday)

I've noticed a distinct lack of POST beeps when attempting to boot with minimal components on the motherboard, should I be receiving any?


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