Desktop won't power up

[prostakus]

My desktop was working perfectly fine, no signs of something dying. It's a new build after all, not even an year old. I left town for a week, after coming back the PC didn't show any sign of life, like it was not plugged in. I started checking everything i could think of. 
Did the paper clip test on the PSU, fan started spinning.
Removed everything except CPU, nothing.
Checked if the power button is not working.
Then I took it apart and rebuilt it again leaving it unplugged.
The next day I plug it in, press the power button and it boots up normally.
After a few hours i bumped my desk and it just powered down instantly, but rebooted again.
To test that I just hit it softly on the top where the PSU is and it shut down again, but this time with a blue screen, but still booting normally and working fine.
The next day it was the same thing over again. Just not powering up.
I noticed some weird things. While it's plugged in and powered down there is a high pitch noise coming from the PSU and when it's unplugged and i hit the power button lights come on and fans try to start spinning and all that is for 2-3 seconds.

The parts are as follows:
MB: Gigabyte F2-A58m-DS2
APU: AMD A10-6800K (cooled with a CM Hyper 212 Evo)
RAM: Corsair Vengeance 8gb (2133MhZ)
HDD: WD Black 1TB
PSU: Fortron ATX 350-PNF (400W peak)
GPU: Sapphire Radeon R7 370 2GB GDDR5 Dual-X

The GPU was an upgrade 2 months ago.

[Xenift]

Well you might have a dead PSU on your hands, possibly even more dead things.

 

Lightning probably struck near your house causing that PSU to fry.

[zyntaxable]

Change the psu ASAP. It's very low quality, and probably not even powerful enough to power your system. It is most likely the problem.

[The_Stig]

That PSU is sketchier than a box of crayons. Replace it .

[zyntaxable]

@prostakus follow your own posts so you see a notification when someone replies.

[prostakus]

Is there any way I can be absolutely 100% sure it's the PSU?

[zyntaxable]

Is there any way I can be absolutely 100% sure it's the PSU?

It is. It's an unknown brand, and unknown brands make very bad quality PSU's. (Bad capacitors etc) You should get a ~500w EVGA g2/seasonic psu. I recommend not starting up your pc until you have a new power supply  because else you risk damaging all your components.

[prostakus]

I will borrow a PSU from a friend and test. Thanks guys.

 

EDIT: I just opened it up. 2 blown capacitors in it.