For a few weeks now the picture has been going in and out. Taking its time to "warm-up" and now the tv all of the sudden would not show a picture. The screen is completely black; although the power light is on. I can use the remote to power the tv on and off. Anthing that I click from the remote allows the green power light to blink. Also there is no sound. The tv is about 5 years old. Please Help