I'm just going from memory here but to tune it, I believe you just turn the detector on, turn the tuning knob clockwise until the sound goes away. Lift the searchcoil about 6" from the ground and slowly turn the tuning knob counterclockwise until you just barely get a sound (that's the threshold point). Lower the coil to the ground and start hunting. When the detector starts "drifting", just repeat the tuning procedure above and keep hunting. The old detectors had a tendency to "drift", it either increases the sound level or decreases it to where you no longer hear it, so that's when you need to retune it and return it to threshold. The old detectors I used usually needed retuning every 5-10 minutes but you'll get used to it.
~Texas Jay
