I used a service remote. (I don't know how or if you can access the service menu without the service remote.) I used access code 0413 to get into the service menu. From there, select System 1, which leads you to a list of options on the right side of the screen. As I recall, dimming was #9, and it defaults to On. You can change it to Off, but lg revolution downgrade from 2.3.6 @ magical, that apk will only read sum of the menu's when loaded on the 2.3.6 V8 firmware it seems to revert back after a reboot you must downgrade to V7 to utilize the lgservicemenu for internal provisioning. .

lg tv service menu code