Computer won't start

So first off this is sad I am posting here since I've been repairing computers for over 15 years and always figure out the problems myself
So here it goes.
Building a new quad core amd
Get everything plugged in and start pc. Starts up a few times so I plug all the cords in and a USB to boot the os. Now won't start and unplug everything and still won't start. Everytime I hit the power button 20 times or so the heating fan tries to turn but doesn't. That's every 20 times or so pressing the power button.
So I take my backup gamer and transfer the mobo and cpu hook everything up. Runs fine plug stuff in won't start same thing. Press power button every 20 times fan tries to turn. But when everything is unplugged where it did start it won't. Any ideas. Thanks
 
The current power supply may not have a 4 or 6 pin AUX 12 volt cord that connects to a connector near the CPU. You must connect this to enable the computer to start
 
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