Two months ago I bought a new build, and I was having a problem with it turning on then back off. This is the help post I made: http://www.maximumpc.com/forums/viewtopic.php?f=35&t=242151
I got an RMA with the MOBO, and a week later, ASUS sent me a brand new board. I hooked it up outside the case with just the CPU, and cooler; and I had the same problem. Changing the PSU had no effect so I knew that the CPU was dead. I went to another store of the same vendor that sold me the parts, and got the CPU replaced, because it was still under warranty. I changed the CPU, and it worked perfectly.
I just got back from being away for less than a week, I turned on the computer, and it turned on then back off, just as it did before. I tried it a few times to be sure, and one time it lasted about five seconds instead shutting off right away. All I have done for testing is unplug the case power, and reset buttons. I am very sure though that the CPU is dead because it is the exact same thing that happened before.
I doubt the problem is the CPU because the computer has worked, and the old CPU made it to POST once so it seems like something is killing the CPU. Also, both my brothers have had good experiences with the same processor, and it seems unlikely that half of the 4670Ks are faulty.
Also the first problem started with one board, and the current one is with a different board; and I have not read anything about Maximus VI Formulas killing CPUs.
That leaves me to believe the PSU is faulty, and is killing CPUs. I do have both the 8-pin and 4-pin connectors plugged in if that could cause a problem. The PSU is a Corsair AX860, and Corsair seems to have a great reputation, but I guess even the best have some mistakes.
Any opinions would be appreciated.
Specs have stayed mostly the same except for the Graphics Card, but here they are anyway:
CPU: Intel Core i5 4670K
CPU Cooler: Cooler Master Hyper T4
MOBO: Asus Maximus VI Formula
RAM: Corsair Vengeance pro (2x4GB)
Graphics: Asus GTX 780
SSD: Samsung 840 Pro 256GB
HDD: Western Digital Black 2TB
DVD drive: LG DVD writer
Wireless card: TP-LINK N450
Case: Cooler Master HAF X
PSU: Corsair AX860