It's probably too late for anyone to see this, but I got an answer from CuriousMarc on the transistors: "The collectors are connected to the cans, but there is

It's probably too late for anyone to see this, but I got an answer from CuriousMarc on the transistors: "The collectors are connected to the cans, but there is a coat of insulator on the heatsinks under the transistors on some models or on the whole heatsink on others, so the heatsinks are electrically isolated from the transistors."