Quoted from RobKnapp:
One Note about LED's installed in Pinball Machines. Made by Bally or Williams. They all have attract mode settings for General Illumination for special effects during Attract Mode. If set to On you will get LED flicker in the Attract mode. I find this annoying. I set my machines to NO: Do Not dim the General Illumination. This setting can be found under A. ADJUSTMENTS MENU A.1 Standard Adjustments . Scroll to A.1 25 Allow Dim Illumination. Set to( No ). Page 1-26 in Operations Manual.
This is an incorrect statement, they don't "all" have these settings. Williams System 11s do not.