Ok, i got 2 old vintage sweep tube amps. onr is a mini scout, the other is a scout 20. there is a adjustment screw on the back of both of these amps (as well as on other old sweep tube cb amps ive seen) with a lock nut on it. what are these for.? how do you adjust them, how can i tell if its right. i know what the tune and load knobs are. i took the bottom cover off of the mini scout and this set screw thing goes into a ceramic peice with a copper coil hooked to it. just dont want to screw these 2 amps up because they are both as new. thanx.