Thanks. There is a dedicated filament winding for the 5U4 for the B++ rectifier. The 25Z6 B+ rectifier is series strung.
According to this label on the back, left side of the chassis and the service info, the "top" of the chassis is hot.
Looks like there's an insulating layer between the top and body of the chassis. Weird setup.
No UL sticker but at least it's a polarized power cord.
