Gecko 201X Adjust Screw
 

What is the function of the Adjust screw at the top of the drive? I searched the manual many times, and can't fine any reference.

Manual only states this:
RESTORING FACTORY DEFAULTS
To restore the G201X to the factory settings set the trimpot to the 11 o’clock position and set SW1-SW10 to “ON”.

On other models like G540 the trimpot is used for midband resonance tuning.

This is from the 203V manual. I think it is for low speed tuning.

ADJUST: This trimpot adjusts the motor for the smoothest possible low-speed operation. Set the motor speed to about 1/2
revolution per second and then turn the trimpot until a distinct null is noted in the motor’s vibration. This will result in the most
even microstep placement for a given motor and power supply voltage. The default setting for this trimpot is at ½ -turn and the
setting for your motor will be within +/- ¼-turn of the default setting.