Re: LG 55LA740V Intermittent backlight band troubleshooting help.
Hi. I am new here.
I don't know if I'm doing it right, putting this thread back. If it's wrong, forgive me and put this answer where it should be.
I have a LG55LA740s tv with more or less the same problem as Mano84 and Heder.
In my case, the vertical dark areas are almost always the same as on their TV, but on other occasions, if we think of 6 vertical columns and we count them from left to right, the dark areas can be 3 and 5 or 2 and 3 or 1 and 6, etc ...
To make it more complicated, I have noticed that the failure increases in winter. The screen turning off leaving only the sound (I don't know if it is a protection system or another failure).
In summer, however, it almost does not fail.
I have seen that Mano84 solved her problem by changing a led strip but in her case it seems that the fault was always in the same place. In my case it is intermittent and can be any strip.
The black and white connectors heder talks about are listed as follows:
Black connector on the left central side of the power board, from left to right: led +, NC, NC, NC, NC, VC4, VC5, VC6 View the front screen, this connector handles the right half.
White connector on the central right side of the power supply board, from left to right: VC1, VC2, VC3, NC, NC, NC, NC, led +. Viewed from the front, this connector handles the left half.
I measured as best I could the voltages on the black and white connectors on the top of the power supply and the most relevant was:
The voltage on the led outputs, with the television being good or bad (with some shadow) is always approximately 87 volts except when the screen turns off completely, then it drops to 71 v.
Outputs VC3 and VC5: The normal voltage is around 10 to 15 volts but when it fails it goes up to 30 volts and when the screen turns off (the sound remains), it seems to be stable again.
I have seen that finally Heder did not tell us if he solved the problem.
Can you give me some idea.
Thanks and regards.
Hi. I am new here.
I don't know if I'm doing it right, putting this thread back. If it's wrong, forgive me and put this answer where it should be.
I have a LG55LA740s tv with more or less the same problem as Mano84 and Heder.
In my case, the vertical dark areas are almost always the same as on their TV, but on other occasions, if we think of 6 vertical columns and we count them from left to right, the dark areas can be 3 and 5 or 2 and 3 or 1 and 6, etc ...
To make it more complicated, I have noticed that the failure increases in winter. The screen turning off leaving only the sound (I don't know if it is a protection system or another failure).
In summer, however, it almost does not fail.
I have seen that Mano84 solved her problem by changing a led strip but in her case it seems that the fault was always in the same place. In my case it is intermittent and can be any strip.
The black and white connectors heder talks about are listed as follows:
Black connector on the left central side of the power board, from left to right: led +, NC, NC, NC, NC, VC4, VC5, VC6 View the front screen, this connector handles the right half.
White connector on the central right side of the power supply board, from left to right: VC1, VC2, VC3, NC, NC, NC, NC, led +. Viewed from the front, this connector handles the left half.
I measured as best I could the voltages on the black and white connectors on the top of the power supply and the most relevant was:
The voltage on the led outputs, with the television being good or bad (with some shadow) is always approximately 87 volts except when the screen turns off completely, then it drops to 71 v.
Outputs VC3 and VC5: The normal voltage is around 10 to 15 volts but when it fails it goes up to 30 volts and when the screen turns off (the sound remains), it seems to be stable again.
I have seen that finally Heder did not tell us if he solved the problem.
Can you give me some idea.
Thanks and regards.
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