DuMont RA113 saved from becoming an aquarium!

[Bill Cahill]

That black color is tar.
I'd check voltages, first.
Hint.
Five volt colors for 5U4 should be yellow.
Plates, red with yellow tracer.
B- brown with black tracer.
primary: both black.
Regular six volt two green.
Other six volt would have been two blue.
You could disconnect filament pin from cathode, install a 6AX4, and, use that.
Bill Cahill