Be careful and don't bump it. I have been using Tesoro's for 31+ years, preferring models with manual Ground Balance, and I can't think of more than two times in almost a third of a century when I have had a GB control get bumped out of a setting.
There are maybe times when some people might have this happen and I can only think of four things. One, they have big hands for the dinky-size micro-MAX (µMAX) or other housings, or wear gloves. Two, they hunt in a very brushy environment and have brush bump against and rotate the GB knob. Three, they just kind of goof and move the wrong control thinking they were adjusting the Sensitivity or Discrimination level, etc.
If any of these things seem to be a cause, there are two things you might try. One would be to get a small rubber washer or 'O' ring from Lowes, Home Depot or most any decent hardware supply store. If you use this method, be careful! Too many times through the years I have detectors where people have used 'O' rings but remounted the control knob too firmly. The result was a control knob that was more difficult to turn, but worse yet was the compression cause know adjustment to also turn and loosen the nut that secures the potentiometer in place.
There have been cases where this has lead to breaking internal wires, contact of wires with other metal components that cause shorting, and made the knob both nonfunctional and loose, and in the case of them doing it with a Discrimination control, the setting references were then not proper for where the knob pointer was.
Decades ago my suggestion to people who have issues with a knob going out-of-adjustment was to simply remove the control knob. The smooth and straight control shaft is much more difficult to 'bump' out of a setting, plus it frees up more space for manipulation around a small control face, and keeps a knob from being bumped accidently [size=small](by man or brush)[/size].
If the smooth knob seems difficult to adjust, just wrap it with a thin layer of tape, or better yet find a rubber 'boot' that will snuggly fit over the shaft. It lets you adjust it, but allows 'space' to help eliminate accidental bumping. That's the method I have preferred for decades instead of using 'O' rings.
Monte
