Zenith Advanced System 3 help needed

[pac.attack76]

Rescued a 27" console tv model SB2777P from 1986 with no video or audio. Just a pop sound through the speakers when clicked off and on. Nothing else except for the same popping sounds when using the channel up and down buttons. Volume can even be increased or decreased but that's it. I want to do a restoration which will include some cabinet work as well. Where should I start looking? Ive worked on many sets before but this one has me puzzled. Seems like the high voltage is out and only getting the low end.