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PC no longer starts - dead PSU or motherboard?

425 views 11 replies 4 participants last post by  Emmanuel 
#1 ·
Hello everyone,

Thursday night I shut down my sig rig normally. I never get freezes, BSODs or other unusual behavior that would point to hardware problems.
However, Friday night I attempted to start my PC and it just "clicks" on for a split second, then turns off, then back on for a split second, and off, over and over.

I pulled out all expansion cards and RAM but that didn't solve anything, I didn't expect it to anyway. I also moved the BIOS switch to a backup BIOS, still no luck. I didn't reset the CMOS or remove the battery because I can't remember if my latest OC settings are saved.

To re-iterate, the computer does not turn on, the debug LED does not show any code and the fans and pump don't even have time to start running. I already ordered another PSU so I can quickly check if that's my problem. I also checked for leaks but there were no signs of water dripping anywhere.

To me it looks like either the motherboard is shorting itself, or the PSU has become defective and is shutting itself off to protect the rest of the computer.

Any ideas?
 
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#2 ·
Wait for the backup PSU and see if that's the problem. Report back here with results. Can't tell anything until you eliminate each cause and the PSU is the easiest thing to eliminate. If you've tried to pull out all expansion cards (including GPUs and tried to run off integrated graphics), then this is your best bet.

If the PSU isn't the problem, then it's probably the MOBO. You'll need to take it out, bread board it to make sure there is no short. But let's not get ahead of ourselves.
 
#3 ·
Integrated GPU is not an option for me so my 1080ti remains plugged in, plus taking apart my water loop is always the last resort. Pulling out the modular PSU was the easiest thing to do so yes I'll report back tomorrow if I receive the new one. I agree with your steps, although I'd be surprised if there is actually a short that it would come from the case. I did some really good cable management, it's properly mounted on all standoffs and the computer hadn't been moved at all since the night before.
 
#4 ·
Remove the EPS-8 and try to turn on the PC, doing that the VRM goes to "no-cpu" and only start the rest of the motherboard. Just to check if the CPU or VRM is making the computer not start

Sorry for the broken english
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#6 ·
While you wait for the new PSU you can test the old one with digtal multi meter if you have one
There should have been a PSU jump starter in the box with your EVGA SuperNova P2 so use that one to jump start the PSU

If it cant even turn on with the jump starter then its dead
What did you order as a replacement?
 
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#7 ·
Quote:
Originally Posted by shilka View Post

While you wait for the new PSU you can test the old one with digtal multi meter if you have one
There should have been a PSU jump starter in the box with your EVGA SuperNova P2 so use that one to jump start the PSU

If it cant even turn on with the jump starter then its dead
What did you order as a replacement?
If you do this please disconnect everything you can cause magic smoke if something is shorted and still connected to the PSU
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#8 ·
I assumed he understood that part but yes dont jump start it while still connected to the PC
Also remember to turn hybrid fan mode off otherwise the fan wont spin
 
#9 ·
Yes it's a full custom loop and no a bad GPU shouldn't cause this kind of behavior. The fact it turns off pretty much immediately tells me it's an electrical problem.

I'll have to check what's in the PSU box. I re-ordered the exact same PSU so that I can swap it in the case. All the power cables are still connected to components and I can't remove a bunch of them unless I take the PC apart. The first thing I'm going to do with the new PSU is just take its power cables, plug them into my old PSU so I can use my PSU tester and test all the rails. Then I'll hook the new PSU in my case and see if it starts. And yes I'll make sure to switch off the ECO mode!

Thanks for your ideas everyone, keep them coming!
 
#10 ·
Quote:
Originally Posted by Emmanuel View Post

Yes it's a full custom loop and no a bad GPU shouldn't cause this kind of behavior. The fact it turns off pretty much immediately tells me it's an electrical problem.

I'll have to check what's in the PSU box. I re-ordered the exact same PSU so that I can swap it in the case. All the power cables are still connected to components and I can't remove a bunch of them unless I take the PC apart. The first thing I'm going to do with the new PSU is just take its power cables, plug them into my old PSU so I can use my PSU tester and test all the rails. Then I'll hook the new PSU in my case and see if it starts. And yes I'll make sure to switch off the ECO mode!

Thanks for your ideas everyone, keep them coming!
The PCI-E has PWRGD signal pin, so the GPU can cause the whole computer not start.

Good luck
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#12 ·
Indeed, that's why I picked the word "shouldn't" haha, because unless it's the GPU itself that is shorting, the motherboard should at least begin to POST and display some LED codes. I'll be damned if it turns out my GPU block leaked water onto my card, but I didn't see any evidence of that so for now I've ruled out a GPU problem.

Here's exactly what happened the night before: turned off my PC and then unplugged my power surge protector to get all the lights to turn off while I sleep. Friday night, I re-plugged the surge protector, gave it a couple seconds and then hit the power button on the computer. That's when I was greeted with this endless start/off/start cycle. I worry that unplugging and re-plugging the surge protector while having all power switches on (on the surge protector itself, and the PSU power switch) may have allowed a power surge to reach my computer, but then if the surge protector does its job, it should have prevented that. Also, my monitor, speakers and some other gear is connected to that surge protector, and they all seem to be working fine.

PS: I tried using a different PSU cable and moving the computer to different rooms but that didn't fix anything.
 
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