Add grid leak and grid stopper resistors?

[Axtman]

I am working on a 1975 Silverface Fender Princeton Reverb. These amps never had grid leak or grid stopper resistors. Should I add them or "not fix anything that is not broken"?

[Jon Snell]

Depending on the chassis number (AA964 etc) the 5C2 apears void of a grid leak resistor, the rest have them fitted. The grid leak is taken care of by the instruments DC resistance to ground, (volume pot).