Not holding a charge + smell of something getting hot

I have a 1979 Airstream Excella and I plugged in my camper for a trip today. A few moments later I heard some popping and clicking in the front fuse box like a fuse was trying to flip. By the time I got my flashlight and inside the camper there was a haze of smoke and the smell of a hot electrical fire but no fire. Doesn't hold a charge but everything runs fine lights, water pump, fans etc and all the fuses are OK.

Did my univolt bit the dust? Any help or trouble shooting would be great.



THANKS!