mark5678,
As long as the incoming signal is 720p/1080i/1080p and the input is not named PC it should work. You may also have some screen adjustment options from the output menu in the cable box that you can adjust also.
What's likely happening is that you're not outputting a 720p or 1080i/p signal from the cable box, which can be adjusted in the settings.
--HDTech
I just purchased this tv and it is connected directly to the cable box with a HDMI cable. When I try to change picture size it will not give me the option to go to screen fit mode. Any help would be appreciated.
thanks

Chowhound
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