I ended up disconnecting that multi-tap power resistor altogether and cobbled a few terminal strips outside this cramped chassis, planning to enclose in perf-metal shield, it fits in the cabinet. I also found a short between plate and screen grid wires pulled too close together on one of the 6V6s, probably caused the initial failure instead of a cap.
A power up today confirmed that after I replaced the four caps in the PS, I need to forget about the radio. Both AM and FM are dead with suspicious crackles indicating IF transformer integral caps have silver mica disease. The stupid compound dial cord is broken in both loops. The amp function sounds pretty good so far, even before the wax-papers get replaced. Most resistors checked higher but within 10%, typical for this age.
All my friend wanted was a good guitar and aux amp, and with record EQ switch, presence control, pair of electrostatic tweeters and pair of 12 inch LF drivers with a 7.5" mid, this promises to be a sweet sounding amp.
Besides, I have two more '57-'58 mono consoles with their original cobra changers, in better shape with the same chassis. Guinea pigs like this one make for easy fixes on these other two
