Chosen Solution
Hi all, it’s my first message for help so please be gentle I have a 40 inch TV (40d420na20) from Insignia and here’s the issue: TV powers on, backlight flickers for a second and then turns offI can see a faint image on the LCD, and sound is OK I opened up the TV for troubleshooting as see the following: Power board shows 12.5 volts on the main rail. There’s only one voltage rail and it is stepped up to around 30-40 volts for the backlightThere are 5 strips of LED backlights, each of these are in parallel with 10 LEDs in each. Therefore, the voltage needed for full brightness is around 35 volts. There is no voltage on the LED connector on the power board.I tested each of the LED strips and they are individually OKI do not see any bulging capacitorsI tried powering up only 1 strip at a time with the power supply, and each of them blinks once before the system shuts off the backlight (1/4 second) Here are the steps I took to try fix: I replaced the main JFET transistor used in the step-up stage - no change Here’s how the power supply looks like:
I have a soldering iron, heat gun, multimeters, and old parts for use and can pull as needed. I can also take additional measurements Any help is greatly appreciated
It turned out that some of the LEDs were consuming too much current, while others were outright dead. I replaced them all and the TV is working again.
