Pull the rest of the tubes, and check the heater pins with a ohm meter. I would bet one is open. And I bet it's the 50L6. Also check the ground connection at the end of the string.
Warren,
Thanks for the suggestion- all tubes good. The schematic shows each tube grounded, am I missing an end of string ground?
Thanks,
Jon
Only one end of the string is connected to B-, the 12SQ7 as it is a series string. If you decide to load this one in the skeet shooter, you can aim it my way :)
TonyJ
Hello again Jon :
I see by looking at the schematic the heater string is just a simple loop. With one lead of your meter on the on-off switch side, go from heater pin to pin 35Z5-50L6-12SK7-12SA7-12SQ7. Has to be an open wire connection at the socket. Did you check the on-off switch itself ?
Warren / Tony
Thanks for the tips, found a broken wire between the heaters of the 50L6 and the 35Z5. It was corroded through inside the insulation.
Jon.