Remove the 5 screws on the PCB and switch. Only 3 screws are visible in the guide. 1 is lost forever and 1 is hiding in shadows.

Carefully pull the control board and power switch off. The knob is fixed to the control board potentiometer. The Stop button is only held in by the control board.

The control board features:

Rectifier

Frequency Divider (produces a period of about 30 seconds)

Stop Button

Simple NPN Switch

Electromagnet (on back)