I thought WTH, i have mentioned this before, but never really SHOWN IT.
https://www.youtube.com/watch?v=Oaw7...ature=youtu.be
I do not consider this to be a real problem, just something rather endearing to this set, for it has always done this since I got it, and it does it not matter if there if no RF input of a good strong signal.
I do wonder sometimes WHY it does it, and if other RCA sets do it also.
Since the IF section on it was jacked up by who ever had it before me, I have put A/V bypass relays in the set, and the sound on this id bypassed right out of the detector 6HZ6 far side of C53, (point 30 ) for external audio by the flip of a switch, and I have noticed it does not do it with external audio.
It's odd, what ever it is! :p