The article discusses one of the problems of modern software - hardware complexes for control of hydrounit  hydroelectricity plant, namely the lack of an embedded system diagnostics of technical state of various hydrounit components . In work present an approach for the implementation of diagnostic systems of one of the most important parts electro - hydraulic actuator  system to control the opening of the wicket gate. The diagnostic model and the basic control chart basic elements of electro-hydraulic converter , namely the main valve and servomotor .

Keywords: Gydroelectricity plant, hydrounit, diagnostics, modeling, control chart, electro - hydraulic actuator.