PC not posting (Fried motherboard ?)

[NewbDavid]

bought this PC used without a gpu and when i first got it I removed everything, cleaned it and then put it back together.
It worked even tho i never installed windows because my hard drive didn't arrive and still has not.
So i just used to logg in to the bois to check if everything is connected and i did that about 7 times or so .
So today my GPU arrived which is a 1050 and i went for a 1050 because it works with almost every 300w psu
So after i connected the gpu (note that I did not test the pc before) the fans from both the cpu fan and the gpu worked but the pc turns off after 3 seconds.
I don't remember but i might have connected the gpu without unplugging the pc.
PC specs :
AMD FX6300
8gb ram @ 1600Mhz
MOBO Asus M5A78l-M LE
PSU LC-Power LC420-12 V2.31 350w

Fixes I have tried :
I unplugged then plugged all the cables
I reseated both the RAM stick and the cpu
I removed the gpu to see if the problem is with the wattage usage and used onboared graphics instead.
reseted cmos
and I have no parts to test which one is the problem but i might get a hold on a psu.
if not the psu, would it be the processor or the motherboard that is the problem ?

What would have gone wrong ??

 

[NewbDavid]

MERGED QUESTION
Question from NewbDavid : "PC not posting"

Maybe replacing the Psu would help ?

 

[COLGeek]

Please ask your question a single time, in a single section of the forum. Use tags to expand the topic.

Also, have some patience. Help will surely be offered in a little time.

 

[boosted1g]

Best thing you can do is test another power supply.

The one you listed is a very cheap low end model. Perfectly possible that even a GTX 1050 is now requiring more power then that PSU can handle.

If you did in fact plug in the GPU without power of the PC then you could have damaged the GPU, the board, or the power supply. You should NEVER plug soemthing in (or unplug something) with the PC still powered on. I even remove power cord (or switch off psu) as an extra precaution.