Question My computer turns on and off, sometimes stays on then randomly shuts off reboots, then fails, then continuously tries to reboot.

Sep 21, 2019
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My PC a few months back started acting up after a power surge. It would randomly turn itself off and on. I assumed it was the power supply that probably was fried during the storm. [I didn't have my APC power supply yet and it was just plugged into a generic power strip] so i replaced it. I bought a tester and tested both the old power supply and the new one. Both passed and the problem persisted with either being installed.

So next i tried the GPU, i unplugged and booted straight from the motherboard without the GPU in the machine. But the problem still occurred. So that ruled that out.

Then, i took the fan off the CPU and cleaned both the fan and the CPU flat side with a lint free cloth and a light amount of rubbing alcohol and reapplied new thermal paste.

When that didn't work, i replaced the CPU completely. It was too new and too high wattage for the old motherboard, so that was replaced as well.

Neither was the problem, so i maxed out the fans my case could hold in case it was a circulation issue. I rebuilt the PC from scratch to see if a short was at fault. Those steps didn't resolve the issue.

Finally, i replaced the memory sticks as that was the only remaining original peice at that point. The problem still occurs. I booted without the case sides on to see at what point it fails. It fails apon booting the CPU.

I also changed the CPU fan.

I was wondering if there were any other potential causes of a computer failing to boot, but sometimes boot... but then shut off randomly with or without load and then try and turn itself on and off repeatedly.

I'm at a loss because it's a completely new machine at this point and the issue is still occurring.

Motherboard: MSI MPG z390
CPU: Intel i7-8700k
Memory: 4 corsair vengeance lpx 3200MHz 8gb cards.
Noctua NH-L9i fan.
6 corsair case fans.
 

Ralston18

Titan
Moderator
From your post:

"I assumed it was the power supply that probably was fried during the storm. [I didn't have my APC power supply yet and it was just plugged into a generic power strip] so i replaced it. "

By the underlined "it", my understanding is that you meant the power supply - correct?

What about the power strip?

Make, model, age? Do you often have power surges?

Do you have another known working power strip to use? Or just plug your computer directly into the wall outlet and skip the power strip completely. And perhaps a try a completely different wall outlet on another circuit.
 
Sep 21, 2019
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From your post:

"I assumed it was the power supply that probably was fried during the storm. [I didn't have my APC power supply yet and it was just plugged into a generic power strip] so i replaced it. "

By the underlined "it", my understanding is that you meant the power supply - correct?

yes its a new power supply.

What about the power strip?

APC backup battery unit is what it is plugged into now. (protects against power surges)

Make, model, age? Do you often have power surges?

Custom build using the components I listed in the thread. It was two years old, but now with a new motherboard, powersupply, CPU, CPU fans and memory sticks its brand new.

Do you have another known working power strip to use? Or just plug your computer directly into the wall outlet and skip the power strip completely. And perhaps a try a completely different wall outlet on another circuit.

I've tried multiple outlets and two different power strips.
 

Ralston18

Titan
Moderator
Look in Reliability History and Event Viewer for error codes and warnings that correspond with the shutdowns and reboots.

Anything you find may be a clue.

Make, model, wattage of the new PSU?

Six case fans? Are those fans installed per the case specifications and guidelines? I.e., the fans could actually be interfering with the intended air flows/paths to the extent where little no air is flowing. Or not flowing where the cooler air is actually most needed.

And even though you redid the thermal paste you might consider trying that again. Use a different paste and be very careful about the application process.
 
Sep 21, 2019
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Ok I'll have to check the log once I get back to my desktop. The processor is an Intel i7-8700 and it is a 95 watt. That's why I changed the motherboard as well. The new and old motherboards are both MSI. The new one can handle the 95 watt processor and specifically designed to run with the i7-8700. I've re done the thermal paste a few times, with different brands. Most recently using the one provided by Noctua. But I'll do the paste again. I put about the size of a pea, but if it was too much you're right it could cause the paste's effectiveness to lessen.

As for the fans there are four that are built into the Corsair case I am using. A side panel fan that is the entire left side of the case. Two small intake fans on the front near the harddrives. An exhaust fan on the back and the two newly added Corsair fan on the top of the case. I may redo how I have the fans as well. I put one circulating air in and another pushing air out thinking I was clever, but that is not to the specifications, so I'll try that as well.
 
Sep 21, 2019
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OK I reset the fans to the case specs. All fans are working and the CPU temp was only at 41 degrees, with little to no deviation from that. Checked all the drivers and bios to make sure everything was up to date. I reapplied the thermal paste and even before I cleaned the old stuff. The old paste looked fine as for the spread across the CPU, no missing areas and no globs of too much paste. Just as an extra step I checked the CPU pins to make sure nothing was bent from my initial install and that too looked fine.

Unfortunately, I couldn't check the logs in time before it shut off. The previous time I booted the logs showed a repeated 6008 unexpected shutdown error.

Once it has the shutdown issue. It tries to reboot and fails at the CPU launch, judging by the LED lights on the motherboard itself, then it shuts down again.
 
Sep 21, 2019
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PSU?

Make, model, wattage, age, condition?
Corsair CX750M 3 weeks 750 watt, brand new.

it also fails with a...

Corsair CX600M 2 years 600watt, like new.

I used both, the issue is the same. I also tested both with a power supply tester. They are both testing at 12V, etc. both passed.
 

Ralston18

Titan
Moderator
Yes - try to view the logs to determine if there is some specific error that corresponds with shutdowns.

"Once it has the shutdown issue. It tries to reboot and fails at the CPU launch, judging by the LED lights on the motherboard itself, then it shuts down again."

Which LED lights? More than one?

I am starting to think that that power surge may have gotten to the motherboard....
 
Sep 21, 2019
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The motherboard is newly replaced, the only thing I can think of remaining is the chassis itself. Maybe the power button is defective. Or the case's cabling has gone bad.
 

Chrushop

Great
Mar 2, 2019
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You haven't mentioned the HDD, especially if it's an Intel SDD, then that would be the problem. My company has experienced many failed Intel SSDs which were RMA'd and failed again! Could be worth trying a different HDD though I think
 

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