I have an old Acoustic 150 guitar amp I've been dragging around since 1975. Powered it up recently, first time in many years, and it still screams just like I remember. The problem I have is that with the volume at zero, I can still hear my guitar. It is not very loud (at zero volume) just wondering if it might be a sign of impending failure. Have same indication on all 4 inputs. I have minimal test equipment, multi-meter, o-scope, tone generator. I would appreciate any help and direction.