PC flickers on and off

[Mxion]

Preface:

 

My custom PC has had a history of power issues. The first time, the original PSU (EVGA SuperNOVA 550 GS) died. Replaced it with the Corsair CX750M. Things worked until a few months leading into October, where these issues happened:

• Monitor would randomly lose connection and turn black. I knew whether or not it would go black while I worked if number pad was locked after booting the PC on. The monitor itself works fine, including the PC (due to music still playing after the screen went black). I've checked and replaced monitor cables, uninstalled/updated the drivers for my GPU, and updated Windows 8.1 to Windows 10. The screen would still black-out after a random amount of time.
• Around the same time, I noticed that the case fans no longer turned on. They worked after being plugged directly into the motherboard, so I figured the case fan hub no longer worked.

Thinking it was power issues again, I bought another PSU (EVGA SuperNOVA 750 G2) as well as some extra RAM (Kingston HyperX FURY 2x4GB). Things seemed to work until I found another issue: my storage drive was no longer being recognized. Because of that, started a Windows update, literally an hour or two after installing the new PSU. Something went wrong while updating, and I couldn't shut it down through the OS, so I shut it down via the power button. What happened after I tried to turn it on again is explained in the next section. I will also note that my storage drive did not make it; I've plugged it into a dock and it no longer turns on.

 

The Problem:

 

The "flickering" issue is, when I press the power button, the PC will turn on for a half-second, then shut off, then on again, then off... It repeats this endlessly until you switch the power supply off. Here are some actions I've taken since then:

• Breadboarded the system. With just the motherboard, RAM, CPU, heatsink, and PSU, the system wouldn't POST.
• Checked the CPU. No pins are misaligned, nothing is burnt out.
• Bought another motherboard (ASRock FATAL1TY Z79 KILLER). This is where it got weird:
  • Testing it before installation, it booted into the BIOS no problem. 
  • After installing, began flickering immediately after pressing the power button.
  • Unplugging all peripherals and SATA connections but still keeping it in the case, it still flickers on and off.
• Getting desperate, I bought another Corsair CX750M from Best Buy to test it one last time. Still flickers.

I'm at my wits end at this point, I can't determine which component is the source of all the problems. I can only guess it's the motherboard, PSU, or maybe the chassis. I plan on taking it to a repair place sometime this week, but I just wanted to see additional opinions/suggestions before I turn it in. Any help is greatly appreciated.

My build:

• CPU
  Intel Core i5-4690K
• Motherboard
  (Old) Gigabyte GA-Z97X-UD3H-BK
  (Current) ASRock FATAL1TY Z79 KILLER
• RAM
  8GB Kingston HyperX FURY (2x4GB)
  (Current) 16GB Kingston HyperX FURY (4x4GB)
• GPU
  EVGA GeForce GTX 960 SuperSC ACX 2.0+ 2GB
• Case
  NZXT H440
• Storage
  Samsung 850 EVO 250GB & WD Blue 1TB
• PSU
  (Old) Corsair CX750M
  (Current) EVGA SuperNOVA 750 G2
• Cooling
  Cooler Master Hyper 212 EVO
• Operating System
  Windows 10

 

[emosun]

logic would dictate it's one of the components you HAVEN' T changed.

cpu is the least likely to fail so we'll save that for last

that leaves the ram and gpu at fault.

flickering on and off is not a typical ram error , so i would blame your gpu for messing with the power supply. that's my diagnosis

[Mxion]

4 minutes ago, emosun said:

that leaves the ram and gpu at fault.

I've tested the system without the GPU plugged in, it still cycles between off and on. I've also taken out all but two RAM sticks--the original ones from when I first built the system. Do you mean leave one stick in and cycle through all of them to test if any are broken?

[emosun]

Just now, Mxion said:

I've tested the system without the GPU plugged in, it still cycles between off and on. I've also taken out all but two RAM sticks--the original ones from when I first built the system. Do you mean leave one stick in and cycle through all of them to test if any are broken?

yes you can try each stick alone if the gpu isn't causing it.

something else (simple i know) but make sure the power button on the case isn't broken , just short the on contact instead to eliminate it as a possible broken button.

[Mxion]

2 minutes ago, emosun said:

something else (simple i know) but make sure the power button on the case isn't broken , just short the on contact instead to eliminate it as a possible broken button.

I'll definitely check the RAM and report back. I've wondered if it was the power button too, but I don't think that's the cause-- as I've turned on the motherboard using the old screwdriver approach and it still won't POST.

[emosun]

also note

the ASRock FATAL1TY Z79 KILLER only supports your 4970k provided it's not using the stock factory bios from when it was first released

 

[emosun]

also did you assemble the machine outside the case to make sure it's not your house having a grounding problem?

[Mxion]

1 minute ago, emosun said:

the ASRock FATAL1TY Z79 KILLER only supports your 4970k provided it's not using the stock factory bios from when it was first released

 

It's a 4690K, though. Does that still count?

Just now, emosun said:

also did you assemble the machine outside the case to make sure it's not your house having a grounding problem?

I did. I also had the PSU plugged into my BackUPS when I tested it. 

[emosun]

2 minutes ago, Mxion said:

It's a 4690K, though. Does that still count?

I meant 4690k.

do this , only have the power supply , and motherboard. no cpu , no ram , no buttons , nothing at all. see if it power cycles in that configuration.

[Chris501]

I know this is a really old post but it's on the first page of google when you type the symptoms but I didn't fully read the post but I just built my new gameing pc it worked for a day turned it off and turned it on the following day and the screen would flicker and come off and on ( even in bios) I had overclocked my gpu the previous day with msi afterburner so I turned of the start up with windows and turned my pic off and it didn't work so I turned it off again let it sit for an hour or so and turned it back on worked good as new and the gpu settings were back to default in msi just thought I would post in case it would help anyone