System not powering 9 out of 10 times

[Prdp]

When I power on my system will turn on only 1 out of 10 times. 9 times only the green light will be there in cpu and fan will run nothing else happen, even mother board logo will not show up.

Everyone said SMPS is gone, so I replaced it will good smps(seasonic s12ii 520), then for first few months it was working fine, now again SAME ISSUE. Really am fed up with this issue

So whats the real problem here, Motherboard or PSU or my power socket(I don't think so)

Note : My motherboard doesn't detects pen drive as well(both in boot screen and in windows)

 

[neosos]

Do you have issues with your electrics in general?
I found that my PSU would start doing what yours did after the power going and coming each month...

I have ordered a UPS to protected the new PSU.