Abstract: A system for adjusting the position of a control member of a power plant has a hydraulic fluid operated hydraulic actuator provided with a displaceable member connected to the control member, and having operating parameters; a servo valve configured to control the hydraulic actuator by means of the hydraulic fluid, and selectively operable between at least an open position for allowing fluid connection with the hydraulic actuator and a closed position for blocking fluid connection to the hydraulic actuator; a by-pass fluid device to drain the hydraulic fluid from the hydraulic actuator in any position of the servo valve; and a control device configured to selectively driving the servo valve as a function of an operating parameter of the hydraulic actuator so as to compensate the fluid drain, and keep the operating parameter within a given range about a selected target value.