I was playing my Archon 50 head today, when I heard some crackling and a noticeable volume drop, which occurs on both channels. Looked at the tubes, all glowing fine. Checked the bias points, and left bias point reads zero, right bias point normal. Swapped output tubes, no change, left bias point zero. Any ideas? It's still under warranty, so I may have to send it in to have them look at it.