Question Cant boot, no beep, PC shuts off <1s after powering up

Dec 17, 2019
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When I am using my PC, it suddenly shuts off, and I can't boot it anymore.
no beep, PC shuts off <1s after powering up, fans light turn on during the <1s

Removed all graphic card, ram, USBs and SATAs. Still same.
Last time this happened, i changed the motherboard and everything worked fine for several months, and it happened again. Is it the motherboard again? Never touch the CPU at all and I believe CPU should work fine.

Tried removing 8 pins cpu power, no beep, but the fans and lights dont switch off until i off the power, I also can smell some burning smell during this process.

Hope someone can help me with this.. It is a disaster :/
 
CPU : 4790k
MOBO : Z97 ASUS MARK 2 SABERTOOTH
GPU : GTX 980
RAM : DDR3 1600
PSU : SEASONIC X-Series 750W GOLD
COOLER : CORSAIR H55 water cooler

Needless to say, a burning smell is not a good sign. Can you identify (roughly) where the smell is coming from without trying to power the system on any more?
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I can't, I got panic and switch off the power right away