I bought a 2 year old system off of someone for $50 and everything was working. A couple days later, I hooked it up and the left speaker didnt work, I suspected wiring so I switched the wires and checked and now neither speaker works. Looking at a couple of options I opened the sub and found a blown fuse. After replacing that I looked at the boards that supply power to my speaker and this is what I saw:

http://s79.photobucket.com/albums/j148/Triggerhappy_111/?action=view&current=P6090256.jpg 

among some other pics which are uploaded to that account. I see the transistor on the bottom left is blown along with the resistor on the right. Is there anything else that I am missing. And what do I have to do to replace these. Is there any certian number I should see to buy a similar type or are they all mostly the same? and what do I have to do to make sure this doesnt happen again? thanks guys for your comtinued support and if you need further information let me know and ill provide it. 

I have the same problem. First there was a buzzing sound coming from the left speaker, and then no sound at all. When I opened up the sub, it smelt like burning nasty, and there was smoke inside. I looked around some but found nothing. I then got on line and saw your post, which led me to check my transitors and find that one was cracked in half and there was smoke residue covering part of the inside circuit. I'm going to try to take it apart and find new parts, but don't know too much about soldering. Did you have any luck with yours?