[Jeffhs]

It could be anything, including the horizontal oscillator being so far off frequency it destroyed the flyback, horizontal oscillator and/or output tube, or even the power transformer, as I am about to explain. I remember reading in a TV repair book from the '60s that, if the horizontal oscillator is way off frequency or not running at all, the horizontal output tube will lose its grid bias, which in turn will overload the TV's power transformer. The latter will burn out in short order from such an overload if the set's power supply is not fused.

BTW, it is a darn shame, IMHO, that the base of the TV was sawed off--many if not most of those older TV cabinets were fine furniture pieces. There are other, much less destructive ways of building a television set into a wall; for example, Heathkit offered several of its 1960s and '70s color TVs in kit form without cabinets (the cabinet was available for purchase separately from the chassis if desired) for just such custom installations, or to be installed in a cabinet of the builder's choice. If it were me, I'd take the set out of the cabinet and build the chassis (with the CRT still mounted in the front bezel with safety glass) into the wall, leaving the cabinet untouched.