No picture, however there is sound

Is this set hooked to cable? Is there a cable or satellite box? When you press the menu button, do you see the menu on screen? Do you see anything on the screen, such as snow, or is it completely black? If the signal is OK and the TV has no picture at all, the red LED on the front of the set should be flashing a certain number of times. If the LED is flashing, the computer has detected a problem in the set and shut the picture off. If this is the case, there is no way for you to bring the picture back by pressing buttons. The number of times the LED flashes is the computer's way of displaying exactly why there is no picture. The set should then be serviced by a qualified tech familiar with Sony TV's. If the LED is not flashing and the menu comes up on screen, check your signal source. If you are using a cable or satellite box, that box could be bad, and if you are using RCA jacks, the yellow (video) wire could be bad or pulled out.