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How to fix a Vizio M420SL Edge Lit LED TV with dark corners

The symptoms are as follows:
Has audio.
Has picture, but is brighter in the center and very dark in all four corners and on the border.
Inputs/outputs all work.
I can see light coming from the back of the TV holes with the back-panel removed.
I checked the power board voltages and everything seems fine. I checked the main board voltages and everything seems fine (not to say I checked everything correctly). I'm trying to figure out why I have the dark corners and borders as it makes it difficult to see anything. I bought an LED driver board from ShopJimmy and replaced it based on another person from YouTube who had a similar problem, but it did not fix the issue for me Can someone provide information as to what may be wrong with this TV and/or how to diagnose it?

Posted by William Jack on


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Edge lit sets have a tendacy of having sections of the backlights bad, there are 4 to 8 zones with about a dozen lamps in each zone, if you have dim edges the outside sets have failed. The issue with replacing them is the lamps get very warm before buring out and in most cases, it damages the defuser panel, so it doesn't spread the light correctly. Start by taking the screen (panel) out and defusing screens and see if the thick one is damaged, either cracked or warped, if it is it's time for a new TV, if it looks ok you can get parts from shoppjimmy.

Posted on Jul 25, 2022

Testimonial: "Thanks for the information. I had already purchased a new TV, but thought it a shame to not try to fix the broken one if I didn’t have to start separating the layers to do it. Was hoping it was one of the boards instead. Thanks again."


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