Is my computer frying graphics cards?

[Mouflon]

About a month ago I bought a new computer and for the first few weeks everything worked fine. Then, seemingly out of nowhere (a was playing a not extremely demanding video game at the time), my monitor goes black and reports "No Signal Detected". I re-booted my computer and after 10-20 seconds the same thing happens, and kept happening every time I boot. Booting into safe-mode, I ran into the same issue.

Switching to the onboard graphics card (an Intel HD Graphics 530), everything worked fine, so I figure it's an issue with the graphics card. I test the card in a different computer, and the same thing happens. So I take it back to the store and they test it, conclude it's broken, and I get a new one.

I install the new card and everything works fine for about two weeks, and then I get the same issue again. So either I've had an extreme run of bad luck, getting two consecutive faulty cards, or somehow my computer is breaking them. What could have caused this to happen and where do I go from here?

specs:
MB: Gigabyte Z170-HD3P
CPU: Intel Core i5-6600k
GPU: ASUS STRIX GeForce GTX 970 4GB
RAM: Corsair 16GB (2x8GB) DDR4 2133MHz
PSU: Fractal Design Edison M 650W
Storage: Samsung 850-series EVO 250GB
OS: Windows 10

 

[Darkseiders]

Only thing I can think of is a bad PCI slot, because that's a seasonic OEM power supply.

 

[Woodini]

You should ask for another card and motherboard and explain them what's happening.If after getting new motherboard the problem stays then it's the psu probably