Hi , I friend recently bought this model with dvd player. He followed the set up instructions but had no sound when the tv was on but sound when the dvd players was on. Both he and myself followed the instruction manual that came with the tv but still no sound. In the end he returned the tv and got another one, again the same thing happened no sound on the tv. Can anyone help me out with this is there a magic switch you need to turn on or something. Please help.