Motherboard repeatedly turns on and off without POST

[reffual]

Specs:

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor
CPU Cooler: Corsair H100i 77.0 CFM Liquid CPU Cooler
Motherboard: Gigabyte GA-Z97X-UD5H-BK
Memory: G.SKILL Sniper Series 8GB (2 x 4GB) 240-Pin DDR3
Storage: Samsung 840 EVO 250GB 2.5" SSD
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive
Video Card: Gigabyte GeForce GTX 970 4GB G1 Gaming
Case: NZXT S340 ATX
Power Supply: EVGA SuperNOVA NEX 750w 80+ Gold
Second PSU for testing: Cooler Master RS-500-PCAR-D3 500w


When booting, my pc will repeatedly turn on and off without POSTing.

Here are the things that I have tried without success:

1. Breadboarding with only the motherboard, cpu, and cpu cooler and one stick of ram (the same thing happens with no ram).

2. Booting with only the psu and motherboard -- the psu fan would spin and stop repeatedly so it seems like the issue occurred even then.

3. Using a different psu.

4. Resetting the bios.

5. Taking out the CMOS battery for an extended period of time as well as trying a different battery.

Based on this, I thought the issue must be the motherboard so I RMAed it. But, the exact same thing happened with the new board. Then, I thought the psu that I was using must be frying the motherboards so I tried the psu on an old computer, but it worked completely fine even over the course of 20 reboots.

At this point, I am completely lost as it seems the only possibility is that gigabyte sent be a defective motherboard with the exact same issue as the old one, but that seems highly unlikely.

I would appreciate any help.

 

[alexoiu]

Try testing the board outside the case, only CPU and CPU fan installed, both 24 and 8 pin power cables connected. No other wires or components. Start the board by shortly touching with a screwdriver the 2 pins on the board corresponding to the case power button.

 

[reffual]

Try testing the board outside the case, only CPU and CPU fan installed, both 24 and 8 pin power cables connected. No other wires or components. Start the board by shortly touching with a screwdriver the 2 pins on the board corresponding to the case power button.

I've already tried that exact setup but the same thing happened.

 

[alexoiu]

Can you post a picture of the board?

 

[reffual]

Can you post a picture of the board?

Let me know if you want close ups or other angles.

 

[alexoiu]

Can you install different CPU cooler and re-seating also the CPU (checking for bent pins)?

 

[reffual]

Can you install different CPU cooler and re-seating also the CPU (checking for bent pins)?

There weren't any bent pins and the problem persisted with the stock CPU cooler.

 

[alexoiu]

Then all that remains is the CPU.

 

[reffual]

Then all that remains is the CPU.

But, even if I try booting without the CPU, the PSU fan will repeatedly turn on and off so it seems like the issue persists even then.

 

[alexoiu]

Are you sure that the PSU does work? Can you test it with different pc?

 

[reffual]

Are you sure that the PSU does work? Can you test it with different pc?

Yes, I tested the PSU with a different pc and it worked fine.

 

[alexoiu]

No other idea, then. Board, or CPu, or... both.
Assuming that there's no issue with the power/reset switches.