I noticed that I was getting some fuzz distortion with my Mesa Bass 400 during rehearsal. I turned it around and could see two of the power tubes with a blueish glow on the inside. When I hit a note, the blue light would flare up a little more. I am wondering if this happened because a while back these discolored power tubes had gotten a little loose and I pushed them back in with my fingers. I guess it is time to call JJ's and do that 6550 upgrade.