John, I think I get it, but not sure. You're saying the motor leads feed the MUX board DC power, but how is the board powered when the engine is in neutral? In my tests here, the headlights and cab lights, which are controlled by MUX, are definitely turning on when when the loco is in neutral. So in theory there isn't any DC power coming through those leads? What is feeding the headlight?
It looks like there's a couple of diodes and I think a red zener diode on the boiler MUX. I'm guessing they make sure the lights are always fed the correct polarity regardless of the motor direction current. And there's a couple capacitors, not sure what they're doing.
Am I getting close?
Also, it looks like your digram (way cleaner than mine, but it looks like I got everything right) doesn't account for the tether connector board having two connectors on the PCB. It confused me because pin 1 on the tender side connector isn't necessarily pin 1 on the boiler side connector. I spent some time matching them up with my meter yesterday and the result is in my drawing.
Thanks for the tips!
