I recently got a 20th Anniv. Tone King Imperial and love the heck out of it. The other night the Lead channel started cutting out when I had the Volume past 4 or so and laid into some loud chords. The Rhythm channel is fine - it's just when I switch to the Lead channel and strike a chord the volume drops dramatically all of the sudden. I'm guessing the problem is a bad preamp tube for the Lead channel, but could use some advice on where to start troubleshooting. I don't see any obvious red-plating, but I'm no expert.