The sound carrier is at 21.75 MC, which my sweep generator WR69 can produce. It traces from sound take off coil at 3rd IF, through both sound IF 6AU6 tubes up to the ratio detector transformer L32.
I can't seem to resize sufficiently to upload the schematic but its here.
Sparton 4940TV.pdf
http://earlytelevision.org/pdf/spart...tv_rider_3.pdf
Still the same symptom, no audio information at full volume, but very loud waterfall when signal is removed. DT box worked fine when checked on the 70 Zenith 16" color TV nearby.
I pulled off the shield of L32 expecting to find a typical, partly-exposed and leaky silver-mica cap. It was not that at all, much more robust and serviceable. Same ceramic dog-bone capacitors as in the picture.
Attachment 205793
Resistors and coils check out individually, what about the mica and ceramic caps??? Shotgun those caps?