Here are the pics showing more detail on the radio. Lots of you have contributed to this knowledge, so forgive me for consolidating it and I thank you all for your contributions. Okay, so this radio has some interesting characteristics. First, the polarity and voltage (and if I am wrong, someone please correct me!): Remove the top cover of the Receiver and one finds a White Pin Set mounted in a Turquoise Socket board to form a sort of Switch. By pulling out the pin set and moving it to cover the 12V, the Receiver is changed to 6V. Likewise on the amplifier, there is swing-away door that exposes another Pin and Socket Switch, relocate that pin set to cover the 12V and the amplifier is switched to 6 volts. Simple, clever and fundamentally reliable and mistake proof.
Now the polarity is somewhat different. I’ll have to draw on the picture in order to show what has faded so much it is not easily visible to the eye. I you look at the drawing afixed to the top of the Receiver cover, and zoom in on it, you will note the left side is depicting how to change the voltage inside the Receiver and the right side is depicting how to change the Amplifier. In the center is a drawing of a second swing-away door on the Amplifier. Open that up and there is a small square Pin and Socket Switch the top of which I have drawn on to show in black what is like Braille in the white plastic. Pull that Pin Set out and aim the arrow towards the black “-” sign and the entire radio set (Receiver and Amplifier) is switched to Negative Ground! I’ll draw on the old drawing as well to make it clear.
I have not read this anywhere and I was quite concerned about finding a polarity switch on the Amplifier without finding a like polarity switch on the Receiver, but the drawing is quite clear (once you study it) that the wiring cable between the Amplifier and the Receiver is managing the Polarity change inside the Receiver (or perhaps, because the Receiver is tube-based it doesn’t care).
So that’s that I believe. Now, unfortunately, I found a broken wire inside the Receiver. (See red-marked wire.) It goes to one of two possible places but I am not good enough to know which. So, I still need to find a repair shop that will go through this radio for me. Any suggestions?