My old Squier BP-15 stopped working. When I plug anything into it, even just a jack with no bass on the other end, I get a huge electric sounding hum and no bass sound. The sound is loud and seems to be affected by the treble knob. Raising the treble knob makes it get louder and harsher. Either way, the sound is always there and I get nothing from my bass. Anyone know what the problem is, and can it be solved for a low price? Or is my amp just fried?