Okay here's a shot of under the transformer. (linked for big)
http://i.imgur.com/TYAlSkF.jpg
I found 3 diodes, and something that looks like it popped, possibly the 4th diode? (look for the question mark near the bottom center of the image)
If it's the 4th diode, far as I know diodes don't just pop like that, so could something upstream pop it?