fusebox

I have a CB radio in my 79 Conquista that i have wired to an open port in the fusebox, the cb has a 2 amp inline fuse and it blew. I guess It blew because it wasnt getting all 12 volts from the battery... Why wouldnt it be getting all 12 volts?

Since I dont have one of those fancy shmancy manuals ya'll suggested I get yet, Maybe one of you with a 79 could take a look at your fuse box, and let me know if anything needs to be a different fuse, and or if anything is missing... I totally don't trust the guy who owned it before me with...