Ok, so the dimmer saga isn't over yet. It turns out that the old King Comm and Xponder do not like a PWM signal for the backlighting. The new audio panel does great with the PWM or pretty much any input signal.
After trying out a few other ideas I realized that I had to go with a voltage-based dimmer for that circuit. I used an oversized (5amp) variable voltage reulator for the dimmer. Controled by a Pot just like the others. I was able to fit everything in the same location as the other dimmer, so I didn't have to rework the panel again. I am using the panel as the heatsink, but am only drawing 1/2 amp, so there isn't much heat. The new dimmer is working great. I just need to order some better hardware than I have at the moment and it is done.
I also rewired the panel dimmer so run off the avionics buss rather than the main buss.
