OK hate to be the bearer of bad news but if you have applied 110 to the DC output of the unit which it sounds like you have, it's toast.
Now for future reference on something like this. The AC side of most stuff is going to go through the power switch and the smaller of the two fuses if there are multiple fuses. If there is only one fuse it will be connected to the AC side. So with a voltmeter, connect one lead of the volt meter to either leg of the switch and the other to the terminals. Do this with the switch turned on. One terminal will be a short or 0 ohms. The other will be a very low resistance. The short is the HOT AC line in and the low ohm one will be the neutral AC line.
IF it's immediately blowing a 15 amp breaker as soon as you put power to it, it's shorted.
Now with the size of that transformer, even having the output of that transformer shorted it would not draw 15 amps from the line. For a 120 to 12 volt transformer to draw 15 amps, the output CURRENT would be 80 or 90 amps and that little transformer is no where near rated to handle that amount of power.
The little pictures on here frankly suck. I can't make heads or tails of how things are laid out on the board at all. I need a good sized top and bottom shot of the board with it turned directly over so that the bottom is the bottom in both shots. Parts side and solder side.
If I had that I would be able to direct you a bit better. But then again, this is what I do for a living.