I swapped the tubes and reset the bias, which was only a bit off for each and was able to settle all 4 settings in at .550 Vdc pretty easily.
Four songs in, I saw, and heard through the speakers, a brief flash on the V7 tube.
Troubleshooting (if you could call it that), I heard a mild hum and scratchy noise in the right channel (only) and reduced output volume. I did some swapping/removal of tubes to deter kine it wasn't a tube and, after searching this site, determined I have a blown 10 ohm bias resistor for V7. It measures open on my meter and even has a small hole in the case.
So, replacing this free little guy is easy, but before I do I'd appreciate any advice/thoughts about what I might have done wrong.
Might this have been an open pin on the new tube Co kd this have caused the bias resistor failure? Is .550 vdc too high? WI of this failure damage the tube? Should test the new tube before reinstalling it to prevent a reoccurence?
Any help woo kd be much appreciated.