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The Insignia set doesn't use backlight inverter boards- it's an LED set, so the power supply board also houses the LED driver board. However- there is a note on Shop jimmy about this model that states the following:
IMPORTANT: The LED strips in these models are prone to failure. If this board does not fix the problem with your TV, it is very likely that you have defective LED strips (part number sj-HD500DF-B57\S0 LED Strips).
The power supply/LED board IS actually showing as out of stock from all of the used/pulled parts vendors out there (and new boards are no longer being made for this set):
You can use the part number for the power/LED board to cross reference on eBay and other used/pulled parts sites to see if one is available. However to determine with certainty that the issue is that board- and not the LED strips within the panel, you need to use a multi-meter to test the power supply outputs (LED +/- pins on the board) to ensure that you're getting 200 volts B+ (DC).
If you test and find the 200 volt line IS present- then it is in fact the LED strips that are the root cause of the issue- and unfortunately those are ALSO showing as out of stock:
Other than that, I'm sorry for the bad news here and wish there were a quick fix.
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