iMac doesnt turn on and fans loud

Hi guys, I got thevimac 1311 a few days ago, it was a few problems:

1. No HDD
2. Lcd conector was broken

So I tryed to turn on the imac and just the first led was on and the fans turn on so loud…a bought another logic board but I have the same problem, just the first led is on and the fans works so loud.

Btw in the HDD I dont have any OS, I dont know if that could be the problem

Ps: I tryed everything to fix the problem, I changed the battery pram, I tryed with shortcuts…