Question PC intermittently won't POST - driving me crazy

Jun 28, 2020
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I built the PC in December. This problem started maybe 4 months ago and has been getting more and more frequent in the last few months.

For seemingly no reason, when switched on, my PC won't POST. Instead the board will power up (with no lights) and the fans will run at a continuously higher rpm than usual. It will fail to POST, with no video output and will just sit there until powered off.

For comparison, when working, the board powers on at a slightly higher fan rpm for a second, then reduces to normal as the board lights up and POSTs with video output.

I don't get how it can be fine for weeks but then have 'bad days' where it won't POST and I'll have to power off over and over as it fails and falls to POST. Only way I can coax it into life is by switching off the PSU using the switch and leaving it for a while.

Yesterday I tore down the PC and did a complete rebuild, everything came out of the motherboard including the CPU and RAM which I reseated in different channels. But alas, it's still doing it.

My next step is to reinstall windows but I'm not sure how beneficial that'll be, I didn't think software was applicable prior to POST.

Any ideas???

Specifications:

  • EVGA GeForce GTX 1080 ti
  • Gigabyte Z390 Aorus Pro WiFi
  • Intel i9 9900k
  • 2* Sabrent 1TB Rocket NVMe M.2 SSD
  • Corsair Vengeance LPX 32GB (2* 16) DDR4 3200 MHz
  • 750W EVGA SuperNOVA 750 G3 PSU
Thanks in advance everyone
 

AJNameS

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Apr 5, 2020
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There can be different reasons. Probably tens..
Why not removing almost everything, and in the end leave the system on only mobo, PSU, cpu and ram...resetting bios via both the cmos and the jumper, if any, and putting them back? I mean really almost everything, even the power-switch cable, in the very end even the ram sticks, with finally leaving it only mobo, cpu, psu to see the aftermath. Instead of the power-switch, a screwdriver can be used.
Ofc, system needs the cmos and the jumper.

Did you throw a look on the cpu socket on the motherboard? Something like a microscope or similar can help there. It's good to check the pins - is any of them bend or even broken/with harder deformation? Bad transportation and too much tightening the screws of the cooler, etc, may initiate a problem, that can be difficult to repair sometimes later on.
 
Reactions: Mandark
Jun 28, 2020
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Trouble is with tearing down the system and rebuilding in stages to see what's working - the problem isn't always present. For example, the PC is working perfectly now, so if I were to rebuild I'd have no clue as to whether it's fixed or instead working until it next fails in a week or so.

And yes i did check the socket when i removed the CPU. Although I didn't have a magnifying glass, all looked in order. The pins looked uniform and in good shape.

This problem's so frustrating because it often doesn't happen and is hard to replicate.
 

AJNameS

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Apr 5, 2020
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What are in bios the current timing (latencies), the voltage and the speed of the ram memory?
And what are the 'natural' timings and voltage of the sticks? I think I saw 16-18-18-36 1,35v somewhere.
And where you live, are there strong vibrations, like someone working with heavy machinery every 1-2 weeks?
 
Jun 28, 2020
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Hello, I'm not great with the technicalities of BIOS so I went in and took some photos which might answer your questions. Please see below link.

View: https://m.imgur.com/a/MlHkh9c


If the link didn't work or you need more info please let me know.

As for the natural timings, again I have no idea lol, how can I find out. My ram is 'Corsair 163301 Vengeance LPX 32 GB (2 x 16 GB) DDR4 3200 MHz C16 XMP 2.0 High Performance Desktop Memory Kit, Black'.

I have XMP Profile 1 enabled but other than that I haven't modified them in anyway - nor the rest of my system.

I don't live anywhere with vibrations so don't think it can be that.
 

AJNameS

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Apr 5, 2020
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Play with the timings, the speeds and the voltage of the ram and cpu. Try to set the things into something like: voltages 1,2 for both, or at least below 1,35; timings 17-19-19-37 or a little higher, ram speed 2666 MHz., cpu speed - stock (3,6 GHz)

The natural timings are what I thought - 16-18-18-36, but you can set them a little higher for now while also changing some other values. This may reduce performance a little, but we can do it initially to seek the condition, in which things are supposed to be longtime stable.
 
Jun 28, 2020
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So you think the cause is potentially the RAM?

I'm happy to do those things although it may take a while before either the problem rears its head again or it never does and it /seems/ to be fixed.

To be clear, when you say voltages, where it says 'Profile DDR Voltage 1.35V' I should change that to below 1.35 volts.

And the RAM timings should be at least 1 unit higher than they currently are , i.e. 17-19-19-37.

Finally the 2666 MHz, could I not disable XMP profile 1 and reach that effect?
 

AJNameS

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Apr 5, 2020
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Well, if things work alright now, just leave them in the current state. I guess you have meanwhile reset bios with the jumper/and/or the CMOS battery? This may have magically fixed things, and if you don't try to overclock something, it all may be just fine from now on.

But if it gets wrong again...
You may have to customize some things in order to have a stable system. I see people working fine with a similar (or same) mobo, with same cpu (I dunno what ram), with voltages below 1,29, and cpu speed not above 4,8 GHz. I have the feeling this mobo is initially made for ram speed 2933 or 2666 MHz, with being capable (but mb not guaranteed to be stable) in higher speeds. Updating bios, if not done already, may also help.
 

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