My best guess is there is something wrong on the other side of the board. I can see no issue in view. Certainly no arcing or red plating that I’m aware of. It looks just like a working amp, it just doesn’t work.
The only area I may have got a bit too hot is between the two Mills resistors, but this is amp #1, the local auction one, so it’s condition was always an unknown. It may have been dead for 50 years for all I know. The one I bought as working still works.
Next I need to figure out how much of a PITA it is to get the board out. Annoyingly the screws for the octal bases are covered by the board, I think I can just get to the one under the input socket, I hope so as I spent so long getting that bloody resistor bent right! If need be I’ll just desolder the GZ34 base. I’ll see if I can figure it out tomorrow. Obviously a huge problem is I have no idea what it should look like, though I should be able to spot blobs, shorts, melted insulation or whatever.