get the sound but no picture

get the sound but no picture

Hello I have a Sony manufactured October 2004 model is KDP-51WS550,I watch DVD s on it ...I can get the sound but no picture and even the sound will stop after a while as if on a timer.. The timer standby continues to flash and the link standby up under it stays on can't seem to get the Video 1 to pop up on the screen..and I have pushed the tv/video button.. what steps should I take please help....

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