Well, it had a moderate raster before the poof. See
http://antiqueradio.org/art/temp/RCA630TS16.jpg .
That's a little hard to judge when you have absolutely no signal, a problem I traced down to a failed 6J6 in the RF section. (It tested OK before, but nothing lasts forever.)
I spent a long time checking my work and poking around. Found one last paper cap that I had overlooked before -- and discovered that one end was not soldered! The lead was just lying in the terminal. In another area I had found a pair of resistors "connected" in the same fashion, so some sloppy serviceman had his hands on it once, but what else is new.
I then remembered that I had seen evidence of arcing from a h-v lead to the chassis, so I disconnected one end and slipped spaghetti tubing over the lead. I also did more cleaning of things in & around the h-v cage.
Oh, and also cleaned the picture adjustment pots on the back panel, something I had skipped before.
I brought it up on the variac and it looks like we're back on track. Raster is back and no spitting, at least for the time being. After some fresh 6J6 tubes arrive in the mail, I'll be able to do some more intelligent diagnosis.
Good to know there's a junk chassis out there -- you never know what odd unobtanium part you might need one day! Reminds me of my Hallicrafters 505, which was complete except for three little coils that someone had "borrowed" once upon a time.