There is a good chance I'm wrong but it would sound logical to me to:
Find the setting you want
Measure the resistance from lug 1 and 2
Replace with appropriate resistor
Then do the same from lug 2 to 3
I can't imagine this would hurt/ fry anything as they are just tone controls.
Give a man a match and he'll be warm for a day.
Set a man on fire and he'll be warm for the rest of his life.