I think my Kenwood amplifier is blown... it doesn't power on when plugged in, and I've tried it in two different cars. I have successfully hooked up a different (MTX) amp in both cars and it has worked, so I think the Kenwood amp is blown. It's two years old... and I checked the fuses on the amp and they're not blown. Could there be any other reason for the amp not working? How do I tell for sure if it's blown?