[bmheise]

Thank you for offering your wiring sketch in addition to suggesting that we draw one up.  Yours saved me a great deal of time and I'm glad I didn't make my own drawing first.
My 37-640 chassis had earlier repair that introduced a wiring fault. From your drawing, Red wire #9 terminates on pin 7 of the 6K7G socket and it of course comes from pin 2 of the 6A8G. 
I found my red wire, (if you can call it that after 83 years) tied to the ground near pin 8, effectively cutting the chassis heater daisy chain circuit. 
I can imagine the repair persons reaction when the radio went from whatever-the-problem to nothing except the dial lamp after they were done.
You sure saved a pretty fair amount of hair pulling on my part. Of that, I'm certain.

Thanks again!