The god folk on s.e.d reckon 1.5V at 200KHz is what there should be as
remnant signal after the L-C filter.
So this is what I reckon happened. The 680nF of the L-C went ohmic
(still measures variously 150 to 250ohm) and lost C so more 200KHz was
passed to the zobel, not made for that level of 200KHz , one of the
paired 4.7R solder points failed with all the heat , then the remaining
4.7R heated up even more.