Analysis of Fault: DKJ Electric Actuator Runs in Only One Direction and Stops When Input Signal Polarity Is Reversed

（1）Check the wiring between the amplifier and the motor. An open circuit in any wire will cause this fault.

（2）When the input signal polarity changes, alternating pulses should appear from the two flip-flops. If no pulse exists on one side, possible causes are:

The transistor is broken down;

The unijunction transistor BT31F is open-circuited or broken down.In this case, the thyristor on the non-pulse side will not conduct.

（3）If the outputs of both flip-flops are normal, the thyristor may be damaged.

（4）The servo motor is faulty.

How to Test and Inspect the DKJ Actuator?

Connect wiring according to the diagram.

（1）Turn on the power switch “1K”. Set the motor to manual mode, rotate the handwheel to move the output shaft to the calibrated zero position (high end of the cam). The milliammeter should indicate 4 mA.

（2）Rotate the handwheel clockwise 90°, the milliammeter reading should change from 4 mA to 20 mA accordingly.If the reading is below or exceeds 20 mA, remove the position transmitter cover and adjust the potentiometer.The rotation angle must correspond to the output current of the position transmitter.

（3）Press button “2K”: the output shaft shall rotate clockwise.Press button “3K”: the output shaft shall rotate counterclockwise.Meanwhile, the output current of the position transmitter shall correspond to the rotation angle.