PC shut down, turns on, but won't boot anymore.

Hello, I was playing a game and my PC randomly shut down (like there was power outage). I turned it on but I just heard loud noise inside the case, monitor was not turning on. I dissembled the PC and dusted it out, after which there was no more noise, but it was still not booting.

After a search online I found an option that let me boot the PC - but I had to remove my GPU (Nvidia Geforce 970) and plug in monitor into motherboard (since it also has integrated graphics). I was relieved that it BOOTS with onboard graphics!

Now can anyone tell me some more things to check before calling it a dead GPU? Is it possible that PSU could be faulty or cable that runs from PSU to GPU? Or something else? I'm in no financial position to buy new GPU so will look into every option prior to that.

Thanks in advance for replies!