Laptops not working

In short. I have 2 samsung laptops, both broken. Both have been opened before. One is stripped of everything besides the essentials (mobo, cpu, ram, etc.) and the other is fully reassembled.

MODEL: NP350V5C

The fans turn on for a brief second then off and then just stay at full speed forever.

Things I’ve tried:

  • repasting,
  • waiting for it to turn on
  • the stripped one got the oven treatment (still nothing).

Please help