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Computer Shuts Off Randomly: MoBo or Power Supply?


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#1 mattbirk

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Posted 03 March 2015 - 10:07 PM

Hello, just looking for support troubleshooting my desktop randomly turning off.

 

Motherboard: ASUS P7H55-M Pro Intel H55 Socket LGA1156 

Processor: Intel Core i5-750 2.66Ghz 8M LGA1156 CPU

Power Supply: DiabloTek PHD550 ATX Power Supply - 550W, 140mm Fan, 20+4 Pin

 

I have replaced the heat sync, because I was getting CPU Fan Alerts randomly when booting in the past, and I have left the PC open for the last few weeks for troubleshooting; all fans running properly, and not overheating. I used Real Temp to monitor the temps. Cleaned the processor of all the old thermal paste as well.

 

It's not the RAM: I have ran memtest, and also done process of elimination...still reboots randomly with all different variants of the RAM. 

It's not the hard drive as I have installed Windows 7 fresh on two different hard drives now...same effects. 

 

Windows 7 reports only half of the RAM I am using; it's 64 bit. I have 12gb RAM, and Windows will state 12GB (5.97 usable). Currently I have 8gb RAM installed (2 x 4gb) right next to each other and Windows only sees 4gb of the 8gb.

 

I am thinking it is motherboard related, but could it be power supply related? I used the Ultra power supply tester and the -5v (I believe) does not light up...but I have had this issues with majority of power supplies I have ever tested, and always shrugged it off. I tested the EPS+12v on the power supply too and it did NOT light anything up at all, but I believe it's a bit different of a plug. I did not test the two at the same time. 

 

Also, there are no bulging capacitors or anything physical that looks damaged.

 

Unfortunately, this is a socket 1156 motherboard which are no longer manufactured and if it's the mobo only want to replace that instead of buying a new mobo/proc combo.

 

Thanks in advance!

Attached Files


Edited by mattbirk, 03 March 2015 - 10:14 PM.


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#2 Citizen_WD

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Posted 04 March 2015 - 03:51 AM

Hello, 
 
This sounds a bit complicated, but I'll try to give you a few ideas: 
If you have a surge protector or UPS - make sure you try to plug in the PC without those, directly to the power source. If not - the method of exclusion is your best bet here. Try another, known-to-work and powerful power supply and keep your fingers crossed. Also keep in mind that the cause may be something simple, such as a faulty power button or a loose ATX power connector. 
 
Best regards, Citizen_WD


#3 mattbirk

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Posted 04 March 2015 - 04:47 PM

I'll try without the surge protector...hopefully that's all it is, but doubtful :)

 

Unfortunately I don't have another power supply, but that's easier/cheaper to replace first, so that's my next move.

 

Also, can someone explain to me what the 8 pin from power supply to motherboard is for? 

Here's the specs

I believe it's the: 4-Pin/8-Pin EPS Connector

 

Thanks!


Edited by mattbirk, 04 March 2015 - 04:50 PM.


#4 YeahBleeping

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Posted 04 March 2015 - 06:30 PM

Hi there .. Here is your answer.  Hope this helps.  Basically its the power connector for a mainboard that supports 8 pin EPS power.  As a side note.. A long time ago when there was only 1 core (cpu) and USB didn't even exist, there was no need for extra power on the mainboard.  Nowadays we have mainboards that support up to 8 cores (technically 8 cpu's) and video cards that require extra power .. who remembers the 3dFX graphics cards that had power cables like a laptop??  Don't need them anymore but they do require a lot more power.  Not to mention powered USB/ HDMI/ etc.. All these newer technologies require more power.  That is why you no longer have a mainboard with 1 power adapter and a psu that only have 4 cables coming out of it.


Edited by YeahBleeping, 04 March 2015 - 06:38 PM.


#5 mattbirk

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Posted 04 March 2015 - 07:03 PM

Thanks,that makes sense.

You think if the 8 pin power is bad that could be causing my issues instead of it being the motherboard? I don't have much plugged in, keyboard, mouse, webcam, HD, 2 DVD roms.

Anyways, thanks for answering my questions about the different pins on the PSU.

#6 YeahBleeping

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Posted 04 March 2015 - 08:32 PM

My best answer for that question is to tell you that low end / weird brand name power supplies - I don't trust them.  Etasis FSP group Corsair Antec coolermaster.  That being said .. I've had an enermax (which is supposed to be a good brand also) catch fire on me once.  Interestingly it didn't take out any components tho.  (yayy) . But I never bought another again.  These brands have been in the biz a long time and I use theirs in my system builds.  I have never heard of diablotek and would be interesting to check their sku against known offshoots.  It could be the power supply.. but it could just as well be the mainboard.  When in doubt.. as stated.. change the psu first.






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