I believe it's a power supply filter capacitor. The amp it started smoking in is a Rockford Fosgate Punch 150 first generation. I was listening to it for about thirty minutes just mix matching my subs to see what sounds best and it started smoking up so I quickly unpluged the the power wire. What caused this? And I don't think anything else burned just that filter cap. It's rated 25v 100uF made by "rubycon" does anyone have any info on this part of a good replacement? I really like this amp and don't want to lose it! Please help..... Maybe the all mighty Perry Babin can help me?