Hi there and welcome to Just Answer. Thanks for asking your question.
Can you tell me the model number of your Samsung. Also, are you using some kind of cable box? If so, what kind - make and model.
Lastly, how are the two connected?
Ok. Both the cable box and the TV have a control to switch the screen ratio. The normal procedure is to set it in the cable box first. Then, adjust the TV's ratio.
The time warner box should have the name and model number on the back - it should be a Motorola or a Scientific Atlanta. That way, I can tell you how to change the ration on the box.
Can you look?
I am not where tv is, but I do know the cable box is a scientific atlanta
Ok. Turn the box off. With it off, press GUIDE and INFO together.
You will enter the set up mode where you can set the aspect ratio of your TV (16:9) and the supported resolutions (you should select 480i, 480p and 1080i).
Then you should be good to go.
Now all HD channels should fill the whole screen and SD channels will have a vertical bar down each side. You can use the Samsung's remote to stretch it.
I will be here if you have a follow up comment or question.
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