Psu+mobo+cpu/hsf.
Nothing else connected....no ram/video card/front panel switches....nothing.
Momentarily short the pins on the mobo where the power on switch was connected.
If it does not power up move the mobo to a piece of cardboard.
Test....if it still won't power up your down to 3 parts.
just bought custom pc built it with my brother, i dont know much about computers at all really, most of the pc is new and was working fine for couple weeks but then turned itself off, i was playing on it and it turned off by itself mid game. i tried turning it back on and nothing, the only way i could turn the pc back on was from turning off the main plug for 10 seconds then turning it back on and the pc would start up. now it has turned itself off again with no errors no blue screens etc all the temps in the pc were around 40c but this time even with the mains plug off and on, it just wont turn on at all! no fans, nothing. the only thing i noticed that goes on for a split second is a little blue LED light on the motherboard. other than that its dead! i've tried removing ram, gfx card, hdds, ssd, even fans and still nothing powers up. is this a motherboard issue or powersupply? or even the case? majority of the stuff bought is brand new. and i haven't knocked it/damamged it in anyway. as i said above i was playing fine and then boom for no reason it goes off. it went off a few time 3-4 times max and then the last time just won't power back again apart from the little light on motherboard for a split second.
what do i do?
thanks.

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