- turn off the monitor (by pressing button 1)
 - press and hold buttons 2 and 3
 - press and hold button 1 (do not release buttons 2,3)
 - press button 4 once (do not release buttons 1,2,3)
 - wait until the screen turns on then release button 1
 - after the service menu appears on the screen, release all remaining buttons (2,3)
 
You can use the joystick to navigate the service menu.
