Computer randomly turns it's self off though temps are fine

Mar 29, 2018
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I've been building computers for over 10 years now and I'm stumped... So I found a good bargain for an i5 3570k, 2x8GB DDR3 Corsair Vengeance and a ASUS P8Z77-V for £150 on eBay and I just had to get it for that price, well I can't figure out the problem but the computer randomly turns it self off and straight back on again though my temps are all fine, below 40c idle and 60c on load.

Everything is set to default, XMP is off and it still randomly crashes, here is the full list of components;

PSU: Corsair CP-9020097-UK VS Series ATX/EPS 80 PLUS Power Supply Unit, 550 W
MOBO: ASUS P8Z77-V
CPU: i5 3570k stock speeds 3.4ghz~3.8ghz 1.25v
RAM: 2x Corsair CMZ8GX3M2A1600C9 Vengeance 8 GB
GPU: Sapphire Dual-X Radeon R9 270X OC 2GB GDDR5 (It's only a 70mhz CoreCLK factory OC)
SSD: SanDisk SSD PLUS 240 GB Sata III

Fresh install of Windows 10 Pro 64bit, changed the mobos battery, tried different power cable, tried different power outlets, have installed windows over 20 times, tried different SSDs, HDDs, tried with GPU in and out, tested all the DIMM slots and done memtest86 over 10 times in all different configurations, I've checked to make sure the CPU is seated correctly and the thermal paste is ok which actually brought me to the attention that the preapplied thermal paste was NOT good, 1/4th of the CPU wasn't even covered by the paste and it was clearly cheap paste but since applying my own (Arctic Silver 5 Thermal Compound) the temps dropped 10c

Symptoms: The PC randomly shuts off completely, no blue screen, just one minute it's on and fine then next it's off and it reboots instantly. I have noticed some other symptoms which are strange, it's almost like Windows will start to fall apart slowly before it crashes, programs will start to crash and not be relaunchable, I've noticed programs like Steam to just crash then when I tried to relaunch it, nothing, Java applications, Chrome, Windows Cortana, various programs. And sometimes after it turns it's self off with no BSOD or anything, when it reboots, some programs don't work and sfc scannow detects problems, rebooting into safe mode and doing sfc again doesn't fix those problems, but after another few reboots everything is back to normal, all programs work fine and sfc scannow detects no problems... This is why I'm completely baffled and can't figure it out... I really need help with this everyone :(
 
Mar 29, 2018
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Well it's brand new and worked perfectly fine for a few months now on the previous mobo, CPU and ram though they didn't use even a fraction of the power: Q9400, 3GBs DDR2 667MHz and some cheap mini ITX MSi board so I dunno if it could be the PSU seeing as it's been working fine for months with another system
 


if the computer is powering off while doing something intensive like gaming then its definitely a PSU problem. if it only blue screens and just restarts back into windows without ever powering off then it is something else

 
Mar 29, 2018
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It happens randomly, can happen during gameplay, while doing nothing, while just watching YouTube or replying to this comment... Yup that happened, using my phone for this now lol
 
Mar 29, 2018
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I'm not actually sure if it powers off, the screen instantly goes black and around 2 seconds later it's posts like normal and starts to boot into Windows
 


does the power light on the tower (case) go out when this happens. do you hear a click when it powers off?

 
Mar 29, 2018
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Well usually I have headphones on so wouldn't be able to hear it and obviously I don't have enough time to check if it's turned off or not, it literally goes from being on and the next second it's black and the bios logo appears instantly, I honestly don't think it's powering off, the PSU is good, I've been using it for months with no problems

EDIT: I've deemed it to be the PSU, I initially thought it was the PSU but reassured myself that it's only a few months old, bought new and was working perfectly fine BUT it's been about 6 hours the PC hasn't messed up once on complete stock configuration, I overclocked the CPU to 4.2ghz 1.24v stable in Prime95 and IntelBurnTest and after a few hours of gaming, general use, it shut off, so I tested it with stock CPU speeds and adding +20 power to my GPU in MSi Afterburner and applying a small overclock, it soon shut off... So I'll just get a different PSU, I plan to get a GTX 970 soon, will a 550w PSU still be ok?

I checked with the CM PSU Calculator and it says recommended would be a 450w but what do you think? 600w?
 
Mar 29, 2018
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It's now happening about 2 minutes into Windows, I can confirm the PC does NOT turn off, it just instantly reboots, either way I've purchased a replacement PSU that shall arrive on Friday, I will update this then
 


one last thought. you said its too quick to notice if the power light turns off but do you still hear the fans spinning when it restarts or does your computer go quiet for a certain amount of time?

 
Mar 29, 2018
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It doesn't turn off, the fans keep spinning and there's no noise difference which is why I personally believe it's motherboard/ram or CPU related because of the strange symptoms where Windows will start to just stop working properly moments before black screen then BIOS logo
 
Mar 29, 2018
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It now happens every few moments after booting, I've currently got the battery out resetting the CMOS, going to boot without the GPU installed and 1 stick of RAM in Channel 4
 
Mar 29, 2018
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Update: It's not the PSU, new PSU, still randomly turns off, so having just 8GB in Channel 3, everything was working fine, stable 4.4ghz overclocking at 1.25v, I decided to overclock the GPU, trying to pump as much power out of the new PSU, 2nd screen started flickering instantly, so put clocks to normal, no flickering, underclocked it by 5mhz on the core, flickering then soon after it being back to default, it turned off, so I thought maybe it's the GPU which is fine because I have a GTX 970 arriving, but I decided to put both ram sticks in channels 1 and 2 and immediately after booting into Windows, Steam failed to load and then poof, black screen then BIOS logo... I'm going to contact the eBay seller and tell them it's the ram, Welp problem solved I guess?
 
Mar 29, 2018
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AHA! IT WAS THE RAM! Weird I did so many memtest86s... In every configuration I could find, memtest86 has currently found 1169 problems and it's only 20% complete.

SOLVED.
 
Mar 29, 2018
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I have isolated the problem, it was one of the ram sticks, I have isolated which ram stick and will be contacting the seller about it and either get a replacement or refund.
 

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