My Vizio 42" LCD tv is showing no picture, it will power on, though. Took it to the shop and they checked it out and said I need a new mainboard. Now the tv will power up and you can see that the screen is getting power but none of the buttons on the tv will work except the power button. Now if I get the part myself, what part number do I need to be looking up, and would it be the main LCD Board, or some other kind of main board? Thks Tavares