HELP! Not sure if my GPU or PSU is dead?

Feb 6, 2019
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So the problem started when i was in the title screen of smite, pc was running fine, i went to another room for like 2 mins, and when i came back the pc was displaying like black and grey squares, in like a carbon fiber pattern, completely frozen, so i had to hard reboot, but when it turned on, everything looked fine, but there was no display, no post, but the gpu fans were running fine, so i suspected the psu wasnt giving enough wattage to the gpu, and was dying or something, since i take care of the gpu, monitoring the temp and limiting games so the temp doesnt go over 60c.
I tried a cmos reset but didnt work.
I went and took the gpu out and tried with onboard graphics, and the pc started fine(but the fans and cpu cooler started a bit slower, and with a false start it didnt do before) i got to Windows and detected everything, so is not the cpu, ram, monitor or cable, so i tried starting it with the gpu on the pci slot but no 6pin, and the display cable on the mobo, and it started and the gpu fans worked, so that discards the pci slot and mobo i guess??
My question is, is it possible the gpu has died (which i hope its not since i take good care of it and its fairly new, its and old he 7770 xfx, but i bought it new like 1.5 year ago from a storage) or its it the psu (or the 6pin), based on the gpu fans spinning without stopping.
I havent tried with other gpu on this pc since i dont own another one, nor can buy another (im scared to try my friends gpu on it, i dont know if its safe?
I cant really test the gpu on other pc since i dont really have another with 6pin, nor my friends do (i live in Venezuela and pc parts are extremely expensive)
Ill try to update if i fine a way to test another gpu or the gpu in another pc, but if anyone has been thru something like this, please feel free to share, if the gpu is dead, am pretty much screwed, but i think i can find a replacement for the psu.

Pc Specs
I5 3470 CPU
Msi b75ma e33 MOBO
XFX HD 7770 1gb ghz Edition GPU
8gb corsair lp 4x2 1600mhz RAM
Omega "800w" psu with 6pin (i know its bad, but it worked for the past 5 years or so, and the 1.5year i had the gpu, also came with the pc so i left it so i had more budget for the Gpu)

Sorry for the long post, but i hope someone can help, thanks.
 
Also, when i tried the cmos reset with the gpu connected, the usb devices didnt turn on, so is it possible the psu making the pc to not turn on correctly, or the mobo detecting an error.
Thought that might help, thanks again.