Please read David Hogg’s excellent comments below. My solution still working great end of 2018.
He dove deeper than I did and got closer to the root of the problem with less side effects. I have not tried his fix since my TV works well enough for now plus then I would have to make a new video.
Thanks to everyone for the comments.
The most amazing thing to me is that no one from Samsung will ‘fess up to this, explain it or apologize to their customers. I guess we’re supposed to throw it away and buy new.
Corporations seem completely unable to get with 21st century and be honest and forthcoming in the face of YouTube and the user community throughout the world.
My 2013 vintage UN60ES7500 Samsung Smart TV began turning itself off and back on immediately about once every 90 minutes, then over a two month period increasing in frequency to every 20 minutes. Power Supply Board good. New Main Board did not solve problem.
Disconnecting Smart TV wire bundle from the main board solved the problem. TV works great now. Using an Apple TV to stream, which is much better and faster than the slow clumsy Samsung Smart TV interface.