I have an MTX 6500D amp driving my 12's in the trunk of the Caddy. Lately, it wouldn't come on when I first started my car while it was hot out, and then after about 15-30 minutes, would start working. Now, I can't get it to come on at all. I verified 12 volts at the power source, at the remote source, and a no-resistance ground. The 3 25A fuses in the thing are fine too. Anything else I should check or should I just write the amp off as finished?