I have a Hartke 3500 transient attack head. When I play low notes or loud notes of any kind, the speakers pop - fizz - crack. When I turn the pots - same story. New cabinet rated at 500 watts - 650 peak. Even when I play an acoustic guitar through the rig - same story. I have read about loose solder joints with this amp. anybody tell me if this is salvageable or even worth messing with. Loved the amp when it worked right.