A power actuator in a hydraulic system is controlled in accordance with an electronic control signal energizing a variable displacement servo pump interconnected to the power actuator. In the hydraulic system, the variable displacement servo pump includes a swash plate directly coupled to and positioned by an electric motor. A transducer responds to the position of the swash plate and generates a feedback signal to balance out the effect of the electronic control signal. A pressurized reservoir supplies a base pressure to the hydraulic system when the swash plate of the variable displacement servo pump is in a neutral or null position. This reservoir is protected against an over pressure by a check valve. To compensate for unequal chamber volumes in the power actuator, a shuttle valve diverts excess fluid from the larger volume chamber to the reservoir.