alternator problem

I'm completely terrified of the electrical forum, but I'm having some problems. My 67 belvedere is not running off of the alt. Anymore, it seems to be running off my battery and draining it. I will go double check both myh alts tomoro. But in the mean time what else could it be?. It was working fine couple weeks ago only thing that's changed is the carb. Last one caught on fire it was really old. None of my wires caught fire or got burned. So I don't think its that. I'm hoping its the alt so I can jus replace it but if not anything else that may cause this???