After the article "Mechanical Workers" published the improvement of the balance lifting system in 1991, the reader wrote to me: "The PT-40 balance crane will damage the machine due to the failure of the electrical system when the lifting screw moves downward. The phenomenon". Last year's introduction was made to improve the electrical system when the lifting screw moved upwards. If it occurs out of control when the lifting screw is lowered, make the following improvements for reference.