Newish Build Not Booting

[Sasstraliss]

Okay. This will be a little bit of a long read. I'll try and format properly, and hopefully I'll remember all the details over the last couple of days. There's a lot to it. I'll try and format this well.

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Two days ago, my new computer build of two months or so randomly shutoff. I wasn't present when this happened, I just found the system powered off. When I proceeded to turn it on, nothing. No fans, no anything. Dead. I take it out into my sunlit room to take it apart and take a look.


What happens when I hit 'On' in more detail...

This may be hard to explain. When I hit the power button, the system will power up (all system fans, CPU fans, etc.) for around 200ms. That's less than half a second. The system shuts off again well before booting occurs or any error beeps can be heard. When the system powers on for that fraction of a second, and then I hit power again, it doesn't happen again. Subsequent power ons result in absolutely nothing, and to replicate the 200ms power on, I have to turn off the PSU and disconnect and reconnect it's power. This made me wonder if it was a PSU issue.


Worth noting...

98% of the times I've tried to boot the computer, it starts up for 200ms and then shuts off. No time for BIOS, beeps, or anything.
2% of the times I powered it on, it either came on for 5-6 seconds or a full minute or less. This was shear fluke and I didn't do anything to induce these occaisions.


Power supply failure? Apparently not.

I meddled around, trying different things. Reseating cables, etc. Nothing worked. I tried using the power supply from that computer to powerup a second desktop setup I had, and lo and behold, it powered the second desktop fine. So it mustn't be the PSU. I tried the reverse, and used the second desktop's PSU to power my non working desktop, and nothing. Guess it wasn't the PSU?


Faulty RAM?

A possibility, and still a possibility. I have no other compatible computers to test the RAM in, but the system uses two sticks of 8GB GSkill 1600 RAM which totals 16GB. So I tried booting with both sticks, no sticks, and alternating each stick. No luck. So what are the chances of both RAM sticks being faulty? Does faulty RAM stop a system in its tracks before it can boot? Does this cause a short which shuts it all off? Can a mobo even boot without RAM or at least stay powered on?


Motherboard failure, surely...

Think again. The same day I did the troubleshooting, I took the motherboard into the store I bought it from. (PCDIY in Adelaide CBD). They hooked up my motherboard to their own CPU, RAM, GPU, etc. It powers on for them absolutely fine.


Back to square one.

So I get home, hook it all up again, and power it on. I'm shocked to see the computer powering on! I look in the BIOS, nothing abnormal. I boot into windows safe mode. It's halfway through doing that when it all shuts off again, and I'm back to the good old 200ms power on I first described. Maybe the ride in the car did it some good?


CPU fault?

I take the motherboard and the CPU in to the store again the next day after more testing which yeilded no answer as to the issue. They test the CPU and mobo together coupled with their own hardware, and once again, fine for them. They had it successfully on for a solid 4-5 hours apparently, no issues.




I'm left with confusion now.

Can it really be the ram? Can both ram sticks be dud? Would bad ram cause this problem?

I've done this testing outside the case to ensure no case shorting. I've tried it with and without the GPU, HD's, and other peripherals.

Also, it's not the power button. I've tested this.

What else can it be?



EDIT: These are the specs:

CPU: Intel i7 3770k (Ivy)
MOBO: Gigabyte Z77X-D3H
RAM: 16GB (2x8) GSkill 1600
PSU: Antec HCG 750w
CASE: Coolermaster HAF920
GPU: Gigabyte GTX670
HDD's: Intel 520 120GB SSD + WD Black 1TB

 

[C12Friedman]

I'm going to suggest you check to ensure your 12v ATX connector is just that and not a PCI connector.
If not that then I would look at the following carefully for irregular contacts. All inserted connectors (ram, gpu if any) and check inside the headers for those to see if there are any loose pins/connectors.
Also, you might try restarting without any of your SATA connectors hooked up to the motherboard, see if you get through POST.

 

[Sasstraliss]

I havn't been booting with any SATA cables connected.

And yes, the 12v 4pin CPU connecter IS what it is. It's not a PCI connecter.

 

[C12Friedman]

I havn't been booting with any SATA cables connected.

And yes, the 12v 4pin CPU connecter IS what it is. It's not a PCI connecter.

Aw shucks, I was hoping this would be an easy one...
I'm thinking a short inside a header possibly or possibly the ram contacts themselves. I had issues something like this (but not this) 23+ years ago, took over a month to figure out (but it was solved). Hopefully this is something easier to identify.

 

[turkeyroast2223]

Make sure your motherboard is mounted in your chassis properly, sounds to me like your mobo isnt grounded, maybe check boot out of the chassis, making sure your properly grounded.

PS. i would also reset the mobo bios (remove cmos battery and put back while completely unpowered) a faulty bios setting can prevent POST

 

[smorizio]

if the pc not the issue (working at the store). have you tried changing the surge suppressor and or the outlet you were using.
you could have a lose wire or bad outlet. or the outlet your on is over loaded. if you have a volt meter check our outlet to see if it withing the us voltage spec. myself it could be two things...there a dead short on one of your cards or the heat sink/mb is hitting the case and shorting out. or the mb has a bad voltage reg and the power supply kicking out when it sensce the short.

 

[Sasstraliss]

if the pc not the issue (working at the store). have you tried changing the surge suppressor and or the outlet you were using.
you could have a lose wire or bad outlet. or the outlet your on is over loaded. if you have a volt meter check our outlet to see if it withing the us voltage spec. myself it could be two things...there a dead short on one of your cards or the heat sink/mb is hitting the case and shorting out. or the mb has a bad voltage reg and the power supply kicking out when it sensce the short.

Good point. The power outlet is fine, I've tested that, but the power cable itself, that's an interesting point. I'll test for that later today. I don't have avolt meter.