Help On/off loop faulty GPU or PSU?

[SheebaV]

Hello everyone. I currently have a problem that I've been trying to fix for awhile now. 2 days ago after I turned off my computer and tried to turn it back on again, it went into a loop of where it would turn on then off again.
System specs:
Mobo: Gigabyte GA P67A UD3P B3
CPU: i7 2600k
PSU: Antec EA 750 Green
RAM: 2x4gb Corsair vengeance
GPU: Radeon 6950
Misc.: Corsair 700D tower, 1tb HDD, H70 corsair water cooler, sound card, all in one + blue ray optical drive, and fan controller
What I have tried to far:
Checked for loose screws, bent plugs, checked power switch if it was simply stuck, re-plugged in the power and reset switches.
Unplugged RAM.
Dusted out everything.
Cleaned and changed thermal paste (AS5)
No weird clicking or sounds I could hear.
Took out battery on mobo for a minute.
Unplugged HDD
I do not have an extra GPU or PSU so I can't swap those out even though swapping out the PSU is the first thing you should do. Also it might be the answer but I'm unsure. I completely took out my GPU and everything runs. No loop. So is it my GPU that's the problem or is it that my PSU can't supply the power? (Can't see screen. Mobo does not have integrated GPU)
Any help would be greatly appreciated. I would breadboard but I am reluctant to do so but I will if I have to. I built this rig in 2010 and is my first custom built PC.

 

[Tradesman1]

First check that the DRAM is well seated, that often causes loops. Also check all the power connections are firmly inserted

 

[SheebaV]

I can't seem to find the reply button on here. I am on mobile so maybe that's why but I tried what you mentioned and I made sure the DRAM is properly set and all the connections are fitted.

 

[Tradesman1]

If that straightened it out, then should be OK, if not, would chack with friends and/or co workers and see if you can borrow a good PSU to test with

 

[SheebaV]

Oops. Sorry I realized I didn't say what happened. The same thing is still going on. It keeps looping on/off after 10-15~ seconds. I'll try to find a good PSU and test it asap.

 

[SheebaV]

So I didn't manage to grab myself a spare PSU, but I was able to borrow a GPU for a short while. I took out my current GPU and put in my friends (Sapphire HD 7870) and it worked like a charm. Booted up fine and everything, screen didn't black out on me even after playing Overwatch and Battlefield. Although this is leaning more towards a problem with the GPU, I didn't have enough time to check whether if it was just because that one PCI-E plug was good and the other was faulty because the 7870 only needed one while my Radeon 6950 needs two. Does this help to signify something?

 

[Tradesman1]

Could still be either, GPU going bad or PSU no longer putting out full power