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1. The valve positioner has an input signal but no output signal. (1) The electromagnet assembly has failed; it is recommended to replace it. (2) The supply pressure is incorrect; it is recommended to check the pressure of the gas source. (3) The zero adjustment of the pneumatic amplifier baffle is set too high, causing the baffle to be far away from the nozzle. (4) Air path blockage. (5) Incorrect gas line connection (including the amplifier). (6) The positive and negative poles of the input signal wire for the electric/pneumatic locator are reversed. 2. The valve positioner has no input signal, but the output signal remains at its maximum level. (1) The zero adjustment of the pneumatic amplifier baffle is set too low, causing the baffle to press too tightly on the nozzle. (2) Nozzle clogging. (3) The output pressure is slow or abnormal. This can cause damage to the diaphragm of the control valve and lead to air leakage, resulting in a situation where a signal is present but the control valve responds slowly; as a result, it is unable to carry out timely adjustments. The solution is to inspect the diaphragm chamber and replace the diaphragm. 3. Poor linear performance of the actuator: (1) The feedback cam or spring is improperly selected or its orientation is incorrect. (2) The feedback linkage mechanism is not properly installed or gets stuck in certain positions. (3) There are foreign objects in the nozzle or baffle. (4) There is a slight leak in the back pressure.