Question Fans spin for a second butPC wont boot

[eelllo]

Hi, I've had my PC for about a year. I built 2 PCs on a budget, both identical.
Me and my little bro built them in a day, got of them running.

My PC has always had a slight "issue" where, when i go to turn it off sometimes it turns itself back on. I thought this was to do with my front panel / signalling connections. I also wanted to add more RAM.

So I opened up my PC, took out ram, put it back in. Then I took off all front panel connections.
When I go to put front panel connections back on the motherboard, it doesnt boot. It just spins the fan if I have the front panel connectors in the right place.

I got a photo from my little bro showing his front panel pin setup, and i copied that exactly. Still having the issue. I did some Googling they say its the RAM, i got lots of ram i changed to loads of different sticks. Nothing.

I have now took, the SSD, HDD, GPU, RAM and put it in my server. It is all working fine.
I jump started my PSU, and that works fine.
So the options left as I see it are : case, cpu or motherboard.
I doubt its the case as the front panel connections do send power when its in the right position.
I cant really see it being the CPU either, so that must mean its maybe the motherboard?

I have checked the board for any blown capacitors or something but there is nothing it all looks fine.
I have took out all my PSU leads and reseated.
Is there a way I can test the life of my motherboard ? OR is there something else I am missing?

IDK if this means anything but when I first built the PC I had the same problem, except this was solved as I wasnt using the extra 4 pin pci style connector in motherboard.. But it all seems fine? My brother suggested maybe a broken wire but they all seem fine...
My PC was literally running one minute then gone the next? I always unplug, turn off and drain power from PC before doing anywork so I cant see how something could of been damaged?
I taken out CMOS battery... What else can I try?

Thank you all who give answers all is appreciated!

 

[rgd1101]

full system spec? include make and model of the psu

 

[eelllo]

Ok,
CASE:CoolerMaster MasterBox Q300L Windowed micro-ATX
PSU:ACE 500W Black ATX Gaming PC PSU Power Supply 120mm Red
CPU: Intel I7-4930K Extreme
GPU: MSI Nvidia gtx 1060 3gb
SSD:Kingston A400 2.5" 240GB
HDD: WD 1TB 7200 RPM
RAM: 2x GeIL GEL332GB1866C10QC 8 GB PC3-14900 DDR3-1866 RAM memory module
Screen: Have 40 inch sony hd tv with HDMI and 19inch prolite e2008hds connected via dvi
motherboardesktop Mainboard LGA 2011 Computer Motherboard USB REG ECC X79 E5 4 Channels

The RAM, GPU, SSD, HDD, 100% work in my server.
The PSU does jump start and work fine.

I may try reseating the CPU but I doubt it will be that.
Like I said, the PC was working 1 minute, I removed front panel connection and some ram, put it back in and its not working... I reseated everything

 

[eelllo]

Well it was the motherboard... So I must of blown something on the motherboard? What is the most common thing to go on a motherboard? Everything seems as new... No blown capacitors or missing connections from what I can see is there a fuse trip or something that gets blown? I