[MrFixr55]

Now that you posted the schematic, I don't know why that Sprague electrolytic cap is across the meter, as it is not indicated on the schematic. It does look "1950"s.

I feel for you, as it is a nightmare trying to trace through the switches. I wish that the tester manufacturer drew a simplified diagram as if the set only tested a triode in the 4 tube socket with 5V on the filament.