Samsung np900x3e shut down itself in 30minutes after start

Hello,

I tried a lot opportunities . Firsty wrote new windows. But problem still was. Latter change thermal compound. But problem still was. So tried other things , tried take out battery and without battery just with power cable. Again computer just turn off after 30min. And couple tested just in bios mode after 31minutes laptop just shutdown. So what kind of problem is ?? Thanks for solution!