SamyGO

I got that "random brightness dimming problem" on my TV also...

Since TV cannot capture any AIR channels. I believe it could be defect. Just call techs for not capturing any a?r channels.
Hey could you ask the technician about what they made defective boards?
Do they throw to trash?
Ask him if you could have defective one for hanging to wall.
It might be useful for me.

Ahh, I am forgetting things quickly this days...
Is being old something like this