lg 42pw450t , wont come on

[garyuk00]

HI HAVE A LG 42PW450T , WAS NOT COMING ON ,, CHANGED THE YSUS BOARD AND IT CAME ON WITH A LOUD BUZZING NOISE, AND IT WAS GETTING HOT ON THE SIDE OF THE YSUS, SO THOUGHT I,D DO A FACTORY RESET, AFTER I DID THAT THE TV DID NOT COME ON AGAIN ,, ACCEPT WHEN I UNPLUG THE YSUS BOARD , CAN SOME TELL WHAT CAUSING THIS AND HOW TO FIX IT
MANY THANKS