I am the new owner of a used G&L L2500. I've dated it to 1998. The preamp wasn't sounding responsive to me like my ASAT, so I opened up the back panel to change the battery and found 2 loose black wires near the bass control pot. I've never experienced a problem like this before. There is a G&L authorized dealer in Madison. I assume best thing is to just take it there for the repair. I don't own a solder gun.