Aria SB-1000 Experts Help. Active circuit gets quiet.

Hey TB peeps,
I picked up an SB-1000 (serial no 104007 so guessing 1981). When I engage the active circuit it has progressively lower output as you turn it counterclockwise (the nasty settings that I wanted the bass for). Anyone ever seen this problem and know what it could be? Ive changed the batteries and no difference. Is it the BB preamp. The pickup works great in passive and the far clockwise setting. Thanks!!
 
Hey TB peeps,
I picked up an SB-1000 (serial no 104007 so guessing 1981). When I engage the active circuit it has progressively lower output as you turn it counterclockwise (the nasty settings that I wanted the bass for). Anyone ever seen this problem and know what it could be? Ive changed the batteries and no difference. Is it the BB preamp. The pickup works great in passive and the far clockwise setting. Thanks!!
Try the Aria club here. Very knowledgeable.