Yes, there's a fuse. On a lot of the big Sovs from that era, the fuse panel is near the bath, but I can't say for sure on yours, mine is a rear bath model, and the fusebox/converter is in the bottom of the streetside clothes closet.
The fusebox is behind the blue door in the front of the Univolt. If your trailer's converter is original, plug in your shore power and just follow the loud hum to find it (seriously).
It is probably the purple or yellow circuit that has those lights. They are in the top right of the fuse panel, and are 20 amp fuses.