After the Agilent Cary5000 photometer is turned on, the micrometer rotates in the direction of the stepper motor, and then gets stuck! The normal state is to turn to the direction of the optocoupler switch, and then turn the grating! Replaced the control board and power board, including the motor that drives the micrometer, and the optocoupler. This is the case. If there are friends who encounter similar problems, please give me more advice, I would be very grateful! Thanks!