This TV had no backlight but would turn on and off. Opening up the back, the power supply HTX-PI420402A had four pairs of wires going to the LED strips. I powered one pair with my LED tester and could observe the splash screen and confirmed that video was good.
I decided to open up the TV to check the strips and this edge lit TV used four sets – one at each side and two along an edge. All strips tested fine with my LED tester.
Shopjimmy sells a repair kit which includes two ICs and two FETs to repair the backlight circuit. I checked the FETs and diodes and none were shorted. Searching the power supply part number on badcaps, there was a suggestion to check the transformer for cold solder joints.
I found a cold joint and there were some clues if I had inspected the board more carefully. There was a scorch mark above the joint on the top of the PCB. The bottom of the PCB had an insulator sheet that had a hole at the cold joint location. And there was a crackling noise coming from the board occasionally, caused by the joint arcing.
Though 90% of no backlight cases are caused by bad LEDs, in this case it was the power supply.
Other models that may use this power supply –