I primarily use this for a practice amp but today I allowed a friend to use it at a gig. As a practice amp I run it at the 25W setting and have never had any problems, however, we switched it to the full 100W for his gig. When we did this the auto biasing would not lock in. We finally got it to respond and when it did I get a red light, two greens and an orange. Amp definitely doesn't feel like it's delivering 100W. Do I need new tubes? I did notice that the power tube closest to the left from the rear was glowing extremely orange.