Sorry for the late reply, but I didn't remember until now.

On these sets I think there's a 1 wire, two pin plug sending 12V from the
deflection board to one of the CRT socket boards (IIRC the green). When you
flip up the chassis it sometimes gets unplugged from the CRT board, and you
can't see it. You also can't see that, for example you are in video 2. Of
course you have no sound.

Hope this helps.

JURB