Abstract: There is disclosed a pilot valve, especially for a servo valve, comprising an actuating motor and a hydraulic preamplifier via which a control pressure difference can be created that acts upon a main slide of a main stage. According to the invention, a blocking mechanism is embodied in the flow path of the control oil. A control duct that is connected, either directly or via a branch, to a control chamber of the main stage can be blocked by manually actuating said blocking mechanism, while the other control duct remains open. The other control duct can be blocked by actuating the blocking mechanism in the opposite direction while the first control duct remains open. A control pressure difference by means of which the main slide can be displaced into a predetermined position can be created manually by actuating said blocking mechanism.

Abstract: There is disclosed a pilot valve, especially for a servo valve, comprising an actuating motor and a hydraulic preamplifier via which a control pressure difference can be created that acts upon a main slide of a main stage. According to the invention, a blocking mechanism is embodied in the flow path of the control oil. A control duct that is connected, either directly or via a branch, to a control chamber of the main stage can be blocked by manually actuating said blocking mechanism, while the other control duct remains open. The other control duct can be blocked by actuating the blocking mechanism in the opposite direction while the first control duct remains open. A control pressure difference by means of which the main slide can be displaced into a predetermined position can be created manually by actuating said blocking mechanism.