LG 49LB5500 LED Backlight Problem..

[budm]

Re: LG 49LB5500 LED Backlight Problem..

https://www.badcaps.net/forum/attach...4&d=1497196012
You MUST follow the steps below, you will be measuring the Voltages at tthe 4 pins of the LED connector.
1) TV is off, then keep black probe on the chassis AT ALL TIME.
2) Keep Red probe on the left most blue wire, then turn on the TV and record what the Voltage goes up to then wait 10 seconds and see what Voltage goes down to then turn off the TV.
3) Move the Red probe to the Black LED wire and repeat the same procedure as number 2 but the different wire.
4) Do the same again for the other two wires (Blue, White) of the LED connector.

[stedmund08]

Re: LG 49LB5500 LED Backlight Problem..

That's great - thanks for such a thorough response Budm!

[stedmund08]

Re: LG 49LB5500 LED Backlight Problem..

Results are in!!!

First Wire (Blue)
Off: 66.8
On: 130-150
Second Wire (Black)
Off: 00.0
On: 15-26 (usually about 17)
Third Wire (Blue)
Off: 66.8
On: 135-142
Fourth (White)
Off: 0.00
On: 00.0 – 00.1

[budm]

Re: LG 49LB5500 LED Backlight Problem..

Results are in!!!

First Wire (Blue)
Off: 66.8
On: 130-150
Second Wire (Black)
Off: 00.0
On: 15-26 (usually about 17)
Third Wire (Blue)
Off: 66.8
On: 135-142
Fourth (White)
Off: 0.00
On: 00.0 – 00.1

OK, you have open circuit in the second LED string, the one with BLUE/WHITE wires.
You can also verify by swapping those two sets of wires to see if the symptom will follow or not.