Been searching for this but haven't found this exact issue.
Several months ago my TV developed a black cloud or shadow over the left 1/3 of the TV or so (see pics). It's not uniform, almost looks like some sort of backlighting burnt out the way it extends across the screen. Picture is still visible through it, and in certain lighting conditions it's not that bad. Everything else still works fine.
Local TV repair guy over the phone said probably the main panel or board, not worth it, but I saw some of the posts here and thought maybe it's just a fuse, or sub-board, or something else easy to fix? Any ideas before I buy a new one?
If the set is LED backlit, some may not be getting power...but I don't know. The LEDs will be along the edge of the panel, unless it was a very expensive set which uses a better lighting scheme, also w/LEDs.
Since there is a picture in the darkness, that may be it.
A FRIEND OF MY GAVE ME HIS I THINK 47" VIZIO TV I TOOK THE BACK OFF AN CLEAN IT UP WHAT THE TV IS DOING IS THIS ONE SIDE IS BLACK AN RED THE OTHER SIDE HAS A RED AN GREEN LINE GOING DOWN IT IT HAS 2 HIGH VOLTAGE BOARD ON EACH SIDE OF THE TV I THINK THE BACK LIGHT R GOING OUT CAN YOU HELP ME FIX IT THI}NK YOU
