During normal operation, the machine functions are normal. Once when not in operation, the headset have slight noise, and the size of the noise can be controlled by the volume potentiometer. Teardown check found after put the keys pressed the motor didn't work, try hand toggle motor, the motor back to normal operation, after repeated experiments found that the motor when turn when not turn like "dead" phenomenon exists. Replace the motor after troubleshooting. If a new motor to replace, as long as immerse motor running a few minutes in the anhydrous alcohol, installed after the dry, usually also can make the machine back to normal.TjRservice manual download site