About the 9905-151
Be advised that when using the control and you have turned the gain potentiometer to the maximum capacity this may not be necessary, due to a wide range of stability conditions the gain potentiometer may need to be adjusted to correct and compensate for the instability.
If you have performed an adjustment where you have set the droop against utility if after you close the breaker and the load begins to surge rapidly immediately shut the unit down. You should always adjust potentiometers slowly so as to not over-torque the unit.
If while operating the control and prime mover the speed-setting on the control does not regulate the speed properly check that the potentiometer is not faulty, initially check if the potentiometer is faulty and replace it with a jumper and setting speed with the main potentiometer.