Atx 8pin power connector issues

[MrTallGuy]

So basically I bought this new power supply because I'm planning on getting a new gpu soon. So once I got the new psu I went to install it and I double checked in plugged everthing right and when I went to go power up the PC nothing happened just a single click coming from the psu.

After 30 minutes of searching the internet and messing with my PC I found out that when I disconnect the atx/(cpu) cable everthing turns on but only for a second not sure why it's only that cable. The psu works just fine intill I plug in the atx cable.

Can someone help me out? I'm stumped.

My PC specs-

PSU(new): EVGA SuperNOVA 850 P2 80+ PLATINUM, 850W ECO Mode Fully Modular

PSU (old): Rosewill ATX 12V 650-Watt 80 PLUS BRONZE Certified Power Supply

CPU: Intel Core i7-4790

MB: Gigabyte GA-Z87X-UD5H Z87 LGA 1150 2-Way SLI Dual LAN ATX Motherboard

GPU: EVGA GeForce GTX 660ti SUPERCLOCKED 2048MB

RAM: Kingston HyperX FURY 16GB Kit (2x8GB) 1866MHz DDR3.

 

[maxwellmelon]

so if you unplug all power connectors except the 24pin and 8 pin connectors on the motherboard will pc turn on then?

have you tried unplugging everything from the psu and preforming the paperclip test?

 

[MrTallGuy]

Okay guys so my motherboard was the one having issues. I took it to two different pc repair stores and they told me that my motherboard was fried. Sad it only lasted a year. Last time I try to save money and buy a cheap one motherboard.