I replaced the smoked resistors and the wax paper caps all at once and the problem went away. Another argument for replacing every paper cap before applying power -- the bad caps apparently can toast things, other than themselves. The resistors in question weren't salvageable afterwards.

Just was kind of surprising to me to see a melted bubbling capacitor with no apparent internal short, and further investigation showing the heat source that melted the cap was not the cap itself, but a nearby part instead. Just food for thought when troubleshooting...