Orange th100 hum pot. What is the purpose?

[Cpounder]

Title says it all. Just swapped tubes and the bias is all good. Still have a decently loud hum. Should I be messing with the hum pot? If so, what should I be looking for. Any info is helpful. Thanks.

[Jondog]

It's for the tube filament AC voltage circuit. Filament wires are a source of hum in a tube amp, and if the transformer doesn't have a center tap for those wires, a false center tap is created with resistors or an adjustable trimpot/potentiometer to combat the hum. Theres no harm in adjusting it, good idea to mark on it where the factory setting is.