RCA CTC4B "Gainsborough" picked up in San Francisco

[old_coot88]

That char contains a lot of carbon which of course is conducive to shorted turns.
After cleaning as much as humanly possible, I would try this before applying any sealant:
With the 3A3 removed, power up the chassis (preferably with a variac) and with the room darkened, look for any sign of incandescence in the cleaned area. Any specks of incandescence would indicate leakage paths between turns.
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(Edit) Why do I think shorted turns would incandesce in this instance? Well, since a couple of turns of wire generate enuff juice to light the 3A3 filament, a single turn ought to light up a speck of carbon white hot.)

And if there's no incandescing, see if any heating can be detected in the cleaned area. An IR camera might come in handy. If there's no heating detectable it's probably good to go.