I got a Phillips 50 inch tv for Christmas. The screen would go black and I would just turn the tv off and then turn it back on and it went away. Lately my tv screen has been going black but still had sound. I unplugged it and rebooted my cable box and it went back to normal. Tonight, I turned on my tv and it was fine and then the screen went black out of nowhere and now the sound is out. What can I do to fix this?