I can't help much but maybe a little. The 76 Sovereign
I worked on this winter is gone along with its service manual. I can try to copy the brake circuit out of my 75 Overlander manual once I get the trailer back in the shop.
We just installed new axles on the Sovereign
. We wanted to test the brake wires before connecting them. On the first test for the presence of 12v
at the brake magnet wire was a no pass. I found a loose ground in the 7 pin connection box in the front of the trailer. Fixed that and all was good.
The brake magnets are proportionally energized by the tow vehicle driver's foot pressure on the pedal, or a full 12v
to the magnets the brake away switch if pulled. The Sovereign brake away switch was powered by the same wire as the tongue jack. But I did not trace or understand where the brake away wire was tied into the trailer brake wire to the magnets.
I bet someone will chime in with more information than I have provided.