I agree with Petefoss. I have the same head unit, and it does have an aux port on the front. I also have an Axxera 40" TV in the RV in the overhead bunk. I checked and it does have an aux port on the back. I think an aux port is pretty common. If your TV has a aux port, the aux cable would do what you are wanting to resolve your sound issue. I know this isn't a "hidden wire" solution. You'll just have an exposed cable running down to the head unit while your camping. Wouldn't take more than a minute to plug in/unplug.
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