This tv had a backlight issue. But when I checked the backlight LEDs, I found that they are good. But after a quick flash, they are becoming dim(Not turning off completely). After the troubleshoot I had to guess that the issue is in the LED driver IC. Unfortunately I was not able to record the troubleshooting steps :-(. I ordered the IC from ebay and replaced the bad IC from the power board. It worked..!
Model Number : 55E18US
If you found the same issue, just replace the IC before you replace the whole power supply. Good luck..!
