I have a vizio 42" lcd that ive had for alil over a year and when i was watching tv the other day it started making a whistling noise then about 10 mins later it stopped and the screen went blank. The tv powers on and everything but the screen wont light up. Im trying to fix it myself but i cant get the back cover off. And trying to figure out what could be the problem. Anyones help will be so appreciated.