Noise bars and faint crackling in audio

[Old1625]

WOW!! That is some display of vertical non-linearity!

Assuming you've covered the input filter caps, etc....

As for the noise bar I'd have a look at the power supply section--paying particular attention to the condition of rectifiers and their connections--but also any power-handling connection, including the on-off switch itself.

If your set uses a rectifier tube such as a 5U4GB in my experience sometimes such a scrolling line can be eliminated temporarily by placing a "beam bender" magnet assembly on the tube and working it around.

If your set uses those dreaded finned selenium rectifiers you need to consider replacing them with silicon diodes. When seleniums "let go" they often emit an unpleasant, flatulent-smelling gas that is poisonous to breathe.

Ground fault in a series filament set can also cause problems like this....