Interesting.Yes, it acctually happened as I was driving through downpour but there is nothing wet in there.
There's a way you can test it: if you complete the fiber optic loop it will turn on. So by removing the AMP1, and putting a piece of FO cable across the connector's two fiber connections (In and Out), the loop will close.
I've included a picture of the connector (the one that comes from the car and goes to the AMP1). You need to find a small length of fiber optic cable and have one end right up against each of the two connection points (on the left of the picture). If you do it right and press the stereo power button it'll turn on *if* the AMP1 is the problem, you just won't be driving the door speakers with no AMP1.
Okay and if you need the piece of FO cable, just PM me