Motherboard Spark, No GPU lights or Display?

[pipesmurad]

Hi all,

13 months ago, I put together the PC below. Everything has worked great until last night. I pressed the power button and nothing happened. Tried again, nothing. This had happened once before, so I unplugged from the wall, waited 10 seconds, then plugged back in and pressed power. This time, though, as the PC turned on, a fizzling, light smoky spark came from around where the PSU motherboard cable meets the board. I shut things down, and inspected the cable. It seemed okay but smelled smokey. Ever since, this is what I notice when pressing power:

The PSU fan runs for 10 seconds, then turns off. All CPU fans, mobo led lights run fine, the WiFi adapter turns on. The Gigabyte motherboard debug code progresses through its typical codes, ultimately landing on the same codes it always has when it’s running perfectly fine. In short everything seems to work fine BUT the GPU does not light up and no GPU fans spin, and there is no display (and I’ve tested HDMI cables).

My only other testing has been to reseat components (GPU, RAM, cables) since I have no backup GPU (and of course the mobo has no built-in gpu) and no backup power supply. Also, the only changes to the PC environment in the past 4 weeks: I bought the 4K display 2 weeks ago and have used the PC without problems just about every day since; and we did just have some electrical issues in the house where one area/ set of switches off one panel has lost power (this panel is not connected to panel the PC is on, though, and no other signs of electrical interference or surging has occurred with TVs, other lights etc).

I’d appreciate thoughts on what has happened, what the problem might be, how to fix, thank you.

Windows 10 64bit
i7-5820K
Corsair - H55
Gigabyte - GA-X99M-GAMING 5 Micro ATX LGA2011-3
Crucial - Ballistix Sport LT 32GB (4 x 8GB) DDR4-2400
Samsung - 850 EVO 500GB SSD
EVGA - GeForce GTX 1070 8GB SC Gaming ACX 3.0
Intel - 7260HMWDTX1 PCI-Express x1 802.11a/b/g/n/ac Wi-Fi Adapter
Corsair - RM 750W 80+ Gold Certified Fully-Modular ATX Power Supply
Corsair - Air 240 MicroATX Mid Tower Case
Display is HDMI to Samsung 43MU6300 4K

 

[pipesmurad]

I asked a couple people today, who said either PSU or motherboard were likely reasons. I also have an electrician checking things in the house and he doubted it was a surge/electrical issue because the same power strip and plug have various electronics plugged in and they had/have shown no visible faults.

Again, any thoughts appreciated on why the GPU is showing no signs of life and there's no display after a spark to the motherboard around where the PSU cable connects to the board. Is it possible one of the cables went bad? Wishful thinking, but if I can try cheaper options before more expensive/complex ones, that would be nice.