I have a se84a amp. When the gain pot is turned, it produces low background static sound. I believe the previous user always played amp with gain at max because that is the point on dial where static is least. The static remains even after gain pot is turned and music plays. I tried a small shot of deoxit red followed with deoxit f5 but it did not help issue. Should I try more deoxit or could it be issue with another part of amp.