Many Quasar / Panasonic, RCA, Hitachi of this era throw off the
hoz osc if the HV got to high. Quick test is to put it
on a variac & try the set at about 100 VAC. If it straightens out
thats the problem. Usually its a shorted pass transistor in the
main power supply.
If you get it going there are 2 other small caps that are must changes
the set. Will cover those if need be.
73 Zeno
LFOD !