Random Computer Freeze - Black screen - Restart

First of all , as a newbie here I'd like to say hello to everybody on this forum and also apologize if this is posted in the wrong section since defacto my problem involves black screen and not a tipical blue screen.

Computer is custom built, all new parts, 5 months old. I became aware of this problem about 2 months after.

My system specs:

i7 4930k - overclocked (bios reset to factory settings later after problem became continuous annoyance)
Corsair H110i GT
Asus Sabertooth x79 mobo
16 Gb DDR3 Corsair XMS3 1600MHz
Evga GeForce GTX 970 SC
Corsair -CS850M 850w , PSU

So this problem has been bugging me for some 3 months now.

Basically what would happen is computer would freeze, if there was sound playing atm, sound would freeze in a "bzzzzz" fashion (continuously looping), 2 seconds later screen would turn black and the computer would restart.
I have disabled later "restart on failure" feature, hoping I would get some information on screen when it happens, but sadly now it just stays on black screen without resetting.

This happens completely random, and so it happens that it is always during some not intensive computing (idle, web browsing, youtube playing, sometimes when working in 3d modeling program -3ds Max).
On the other side, it never happened when computer was doing some intensive 3d rendering or gaming - coincidence or not, I don't know yet...

Biggest problem now is that I'm still unable to recreate the event. I've tried forcing both CPU and GPU with tests for hours&hours, and everything would be successful, and then next day or in a week I would start the computer like today, opened chrome and out of nowhere it would freeze w. black screen.
Btw, I've used Prime95, Intel Burn test (on very high), Cinebench, FurMark and Heaven Benchmark.
I have tested memory with Memtest 86 for about 4h and it was ok, zero errors. (I realize this is not nearly enough time to test, so will repeat it again for 12+ h)

Initially I've associated it with power failure due to the loose main power cable on PSU, but since I corrected that and continued to experience this problem, then I started to suspect my OC settings.

So I switched BIOS back to default factory settings (didn't take the battery out) but it happened again.

I know for a fact this didn't happen before my first OC attempt and fiddling in BIOS (although I started OC about a week after the computer was assembled) , but I want to see now if some hardware piece went haywire in the meantime (or was faulty to begin with) or something else ?

As said, mentioned event would happen completely random, so far about 1-2 times in a week.

Event viewer gives me this log :

Critical - (Source) Kernel-Power - (Event ID) 41 - (Task Category) 63
EventData
BugcheckCode 278
BugcheckParameter1 0xfffffa80112144e0
BugcheckParameter2 0xfffff88008411978
BugcheckParameter3 0x0
BugcheckParameter4 0x2
SleepInProgress false
PowerButtonTimestamp 0


So far I have around 20 of these events, but I realize that they are mixed with standard instability crashes (with blue screen) which I had earlier while OC-ing.

So do you guys think this is likely a hardware fault ? Would it be likely PSU (CS850M is not so prized anyway), or a motherboard or something else ?

I do have another spare PSU, it's a very cheap, no-name unit, but it has 500w and technically would be enough to drive the system (PSU calculator estimates around 410w for my system). Should I try it ?

I'd really appreciate any help / opinions.

Thanks in advance !

Sorry for the long read, but I've tried to be as much descriptive as possible :)

p.s. If there will be need, I can post also my OC-ed BIOS settings, although I don't think it matters now since it has been reset.

Update regarding memory testing. Just finished 10+ h of Memtest86 with 0 errors. Should I run it more ?

Bump !

Id really appreciate any input guys, after 3 months this is slowly starting to drive me nuts !

hi - just some random comments, as i commiserate with you 'cause i'm trying to revive my mom's computer, 6,000 miles away.

i agree all your tests of hardware don't show much evidence there. I suppose it could be power - id see if you can just swap for a warranty replacement, if your no-name PSU shows it's bad. But i'd try my last point first.

You seem to eliminate the graphics card by your comment about rendering (which in itself is not graphics intensive, if you're writing to disk, and not previewing) but any gaming should be a graphics-suspect.
Likewise, if you're modeling, in real-time full shaded-mode preview in 3DS, that should be both graphics and floating-point intensive.
So finally i would look to browsing, which, to me is the most suspect of all environments.

How 'bout dumping chrome for a while - use Firefox, or even 32bit safe-mode IE.

see what you get -

2¢

Hi , ok thanks man for suggestions.

So yeah, graphic wise, although rendering itself doesnt use gpu, it is used when navigating in viewport and also when doing some real time rendering. This uses it actually as hard as FurMark running for 40-60min.

So far what I've did is updated / reinstalled all motherboard drivers including Asus AI Suite 2. Originally I didnt want it so I deleted it, and I specifically remember that as soon it was removed, I got my first unusual crash (bsod on clicking finish on app uninstall) - stupid but I got a funny feeling it could be connected.

My last crash was 6 days ago, if it will happen, it will happen in the next 5-6 days. And if yes, then I'll try swapping PSU-s.

'bout your last point , I really didn't know that browser could also be responsible for smth like that. I guess I can try switching to IE (as its most native to windows) , if crash repeats.

I'll update this thread when I know something more.

p.s. hope you managed to revive your mom's computer :P

Quick update , don't want to curse it , but it's been 12 days now and crash didn't happen . On average, it would happen at least 1-2 by now. What I have done is reinstalled motherboard drivers including
Asus AI Suite II .

The most crazy thing is this, I remember I uninstalled AI Suite in the first place couse it was sometimes giving me some crazy warnings like VCore jumped to 3V or something. As soon as I uninstalled it , still in windows I got a Blue Screen Of Death. Don't remember exactly, but this could well be the point since all this black screen restarts started happening.

Didin't swap the PSU yet, that was my next plan in case crash happens again but so far... (knock on the wood).

Will post if it comes back.

Cheers !