trumpet 5,000+ posts
Barry Schanz
You have a whole list of issues to fix here, not just the box. I'm guessing you have numerous weak points in the electrical system that we don't yet know about. I would suspect everything at this point, your grounds for the battery, the wire connecting your alternator to the battery, the current capacity of your amplifier's power wire, the quality of the amplifier's ground termination. I wouldn't even bother playing the amp until you get the electrical issues sorted, and then your next problem is the massively leaking box. A sealed box needs to be 100% free of air leaks. Even a pinhole leak can cause a change in performance. Poor quality wood will leak air right through the pores.