My push-pull 6V6 amp is having an issue of one tube glowing bright orange and reading a significantly lower voltage than the other when sitting idle. If I play the amp, the more I push it, the more stable it becomes. It's also reading about 10-15v higher on the screen than plate on both tubes. Checked the PS caps, rectifier, tubes, sockets, screen load resistors, grid caps, switches, all phase inverter connections and parts and nothing is wrong. As I was inspecting things while it was running, I watched as the cathode bias resistor on the 6V6's desoldered itself and fell off. A couple seconds later, the bypass cap exploded like a gunshot sending fuzzy paper all over the bench and amp. The bright tube has changed from one tube to the other a couple times, too without any changes being made, just between test power ups. It's a Mercury OT and they're pretty sure it's not a problem there, and I tend to agree. PT problem maybe? It's a stock Orange that was fried and rebuilt by TDS. Funny thing, this amp has been working fine for a couple months, then just started doing this one day.