I can see the dimming, but it only happens when certain playfield features are activated. There is a higher degree of dimming when the pop bumpers and flippers are activated, and less dimming when the center bonus whole is activated. I don't see any dimming for the slingshots, rollovers and side bumpers. It might be related to some switches at the beginning of the power circuit for these playfield features. Check the following switches to see if they are clean and adjusted properly:

#2 start relay switch - white wire and grey/white wire
Game over relay switch - grey/white wire and grey/red wire
Tilt relay switch (2 switches) - grey/red wire and grey wire