My buddy has a Silverado that was having some issues. Whenever there was high frequency, it buzzed. It was not the horn, we took that out and it still buzzed. The speakers weren't blown, I've blown a lot of speakers, and this was not it. It was something in the head... So we took it apart. And don't you know it, we didn't fix it. It sat for months and I need to get it back together for him. Does anyone know where I could find a wiring diagram for the speakers/head AND does anyone have a clue what may be causing the noise? Bad tube, maybe?