K, as it happens there was nothing wrong with the flyback. As usual I induced my own fault during cap replacement, a glob of solder had dripped down and lodged itself on one of the background pots. That caused all the B+ boost voltage to be shorted to ground via a 10k 1/2 watt resistor, which eventually cried uncle to let me know where the problem was. That was the source of the smoke that looked like it was coming from the cage.
Removed the solder glob, replaced the 10k resistor, and put a new damper in as a precaution (it went cherry on me from the short). Here's what the replacement can caps look like in the chassis.
