This latest RSF (roadside find) is a 50 inch 4K model built in 2016. It has 3 HDMI inputs. Screen appears to be intact.
In searching around it appears to have an endemic problem that it will not power up. Cannot get backlights to turn on. Appears to have a power board just for the backlights. Anybody have any experience with these? Thanks.

more than likely main board and bad leds.

The front panel LED cycles on and off every minute and a half. Can't see the logo with the flashlight test.
So, it might be a PS problem. Thanks.

This latest RSF (roadside find) is a 50 inch 4K model built in 2016. It has 3 HDMI inputs. Screen appears to be intact.
In searching around it appears to have an endemic problem that it will not power up. Cannot get backlights to turn on. Appears to have a power board just for the backlights. Anybody have any experience with these? Thanks.

You see that huge heatsink on the main with the two depressions? Under those depressions are BGA chips. They need to be reflowed.

Unfortunately, the reflow temperature is close to the fail temp of those BGAs. The other problem is that the board has several electrolytics which don't like heat, so if you decide to preheat the board (good idea), remove the electrolytics from the board and preheat the board at 150F for an hour to drive moisture from those BGAs so they don't "popcorn". Reflow immediately when it comes out of the oven.

Do the reflow with hot air at 480C arriving at that temp over a minute ramp-up, then hold that temp for 10 seconds.

Throw TV out when that doesn't help .. :D

John

Re-balling video:
https://www.youtube.com/watch?v=U-WxVz1f5LI
The guy wants $130 to do mine. I think I can do it for less. Can you use a heat gun?
Got to figure out how to get the heat sink off first.
I've got a friend who has the 65 inch version of this and I know he'll ask me to look at it when it craps out.