How Do I get PBS back on my DTV?

I just got a flat panel DTV. I don't have to use my Digital Converter Box anymore. As I set the tv to do the auto tune, it shows that it can not get PBS at all! Is there a way to get it on the TV so I can watch it? Or better yet, have the Auto Tune pick it up so I can see it. I like NOVA and This Old House.