I bought a 67 bandmaster from crusty cabs a month and a half to 2 months ago. When the amp arrived I didn't have a speaker cabinet, so I went to guitar center to plug it into a marshall cab of theirs just to see if everything was fine. Completely quiet. Everything working fine. Finally I got my speaker cab yesterday, hooked everything up and turned on the amp. when I switched it off standby there was a fairly loud 60-80 cycle hum. I turned it off unplugged my cable, turned it back on same thing. There was also a cracking/sputtering noise that faded in and out. I tried different outlets in different rooms, different cable, tried all 3 positions of the ground switch, etc. Still no luck. When I bought the cab I was told that it had been fully serviced, and he is a very respected cab builder so I wouldn't think it was a cap issue. And it hasn't been played on or moved in about a month. any advice would be helpful.