My Vox AD50VT amp has no sound?

My Vox AD50VT amp has no sound. It powers on fine, but sound doesn't come out of speaker or headphone jack. I ran some music through the line-in to see if the sound would work, but still nothing. I opened her up and looked for obvious problems as well as tapped and wiggled this and that to hopefully find a short. I tried resetting all the settings already. The next thing I will try is to replace the preamp tube. My question is: What else should I check out?