Unless I have the models really mixed up there should be two separate board, the controller board and the voltage regulator board. The VR board has 3 pots; stability, which does what it sounds like; volts, which sets the voltage; and volts/Hertz, which sets the cut in and drop out or the frequency at which the regulator quits trying to maintain output as the engine slows down. I think the same AVR was used across a range of the little units and the controller board is the one that doesn't have any adjustments, just test points. But then again I could be out in left field and have several makes and models confused. I would dig out the service manual and my meters if it were mine.The inconsistent symptoms sound like the AVR pots might be dirty or corroded from sitting and the vibration of running again has them acting intermittent. The service manual will tell what output to look for and I would turn each one through its range, return them to the starting point where I found them then follow the manual to nail the adjustment.