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[Solved] LG 42LB650V - Black Screen, Audio Issue: No Backlight, Power Supply Board Replacement

kar-bau-kopec 19545 13
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  • #1 17162278
    kar-bau-kopec
    Level 7  
    Posts: 6
    Rate: 8
    Hello, I'm after electronic school, but unfortunately I have never worked in my profession. I still remember Conieco and I have a question. After switching on the TV has no sound but no picture. I read similar topics. Image after highlighting the flashlight is. I read that it was the fault of the power supply that does not give voltage on the leds. I bought the whole power supply board at auction (used-seemingly functional) after attaching the same. There is no voltage at the backlight output. Question, should you always see tension after switching on? Is it still controlled from the second board? Maybe someone had a similar problem and can tell what could be the reason? Thank you in advance and best regards. daniel
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  • #2 17162322
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    Hello. Identify the power supply and matrix
  • #3 17162332
    kar-bau-kopec
    Level 7  
    Posts: 6
    Rate: 8
    Power supply EAX65423701 (2.0). I don't know where to read the matrix designation
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  • #4 17162348
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    And such a sticker is on the metal matrix housing with the mark. LG 42LB650V - Black Screen, Audio Issue: No Backlight, Power Supply Board Replacement
  • #5 17162359
    kar-bau-kopec
    Level 7  
    Posts: 6
    Rate: 8
    One more number I found on the housing is: MCR65227506
    Attachments:
    • LG 42LB650V - Black Screen, Audio Issue: No Backlight, Power Supply Board Replacement 15234671078472082394921.jpg (2.74 MB) You must be logged in to download this attachment.
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    #6 17162368
    itadek
    Level 23  
    Posts: 827
    Help: 47
    Rate: 227
    Check buddy, the same LED backlight in the matrix? What voltage on leds when switching on the tv?
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    #7 17162372
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    Your TV model is LG 42LB650V. So correct the title first. And the matrix model is inside I showed a photo.
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  • #8 17162388
    kar-bau-kopec
    Level 7  
    Posts: 6
    Rate: 8
    Voltage at 60V on. After a while it drops to 0

    Matrix No.
    494K75M7LCZZ-ZZ6680
    AU42H100RZTW8CN2E9HB0M2
    815942T4900149H000M0161DOLE02
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    #9 17162405
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    Somewhere you have a burnt LED on the backlight bars. I would advise you to hand over the TV to the RTV point. I don't know if you can disassemble the matrix and break it down, not a problem to get to the lighting strip.
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    #10 17162430
    itadek
    Level 23  
    Posts: 827
    Help: 47
    Rate: 227
    Bingo also suggested so, after repair proposes to reduce the level of backlight in the image menu every time after such a fault I had settings for 100% power, good luck
  • #11 17162436
    kar-bau-kopec
    Level 7  
    Posts: 6
    Rate: 8
    Thank you for your help. The last question, what could be the cost of replacing such a strip on the site? Indicatively
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    #12 17162446
    Pedros050
    Level 43  
    Posts: 17906
    Help: 2471
    Rate: 3901
    And this is how these strips look after stripping the matrix. LG 42LB650V - Black Screen, Audio Issue: No Backlight, Power Supply Board Replacement Each website counts differently is difficult to say?
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    #13 17162734
    E8600
    Level 41  
    Posts: 8864
    Help: 525
    Rate: 2475
    You got here like "Foreman" repaired the same TV model. Take care and don't make the same mistakes. :)



  • #14 17162951
    kar-bau-kopec
    Level 7  
    Posts: 6
    Rate: 8
    Good advice ;)
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Topic summary

✨ The discussion revolves around an LG 42LB650V television experiencing a black screen and audio issues, with the user suspecting a faulty power supply board. After replacing the power supply board, the user still observed no voltage at the backlight output, leading to inquiries about whether voltage should always be present and if the issue could be controlled by another board. Responses suggest checking the LED backlight for burnt components and recommend consulting a repair service. The user also inquired about the potential cost of replacing the backlight strip, with suggestions to reduce backlight settings post-repair to prevent recurrence of the issue.
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FAQ

TL;DR: LG 42LB650V black screen/no backlight? After repair, avoid "100%" — "reduce the level of backlight" to extend LED life. [Elektroda, itadek, post #17162430]

Why it matters: It helps LG 42LB650V owners and repairers focus on failed LED strips, avoiding needless PSU swaps.

Quick Facts

How do I confirm the backlight is dead on an LG 42LB650V?

Shine a flashlight at an angle onto the screen while powering on. If you see the image, the LCD works and only the backlight is off. This simple test separates backlight faults from other failures. [Elektroda, kar-bau-kopec, post #17162278]

What does a brief ~60 V that drops to 0 V on the LED connector mean?

It shows the LED driver attempts startup, then cuts output. In this case, voltage reached about 60 V and fell to 0 V. That pattern points to a backlight strip fault rather than a stable power supply output. [Elektroda, kar-bau-kopec, post #17162388]

Is the power supply board EAX65423701 the cause of no backlight?

Often not. A member diagnosed a “burnt LED on the backlight bars,” which prevents backlight even with a good PSU. Replacing the power board alone will not restore light if the strips are open or shorted. “Burnt LED on the backlight bars.” [Elektroda, Pedros050, post #17162405]

Where do I find the panel (matrix) model label in this LG?

Look for a sticker on the metal matrix housing. That label carries the panel designation used for service references. Inspect it before ordering LED strips or parts. [Elektroda, Pedros050, post #17162348]

Should I attempt to replace the LED strips myself?

It is delicate work that requires full panel disassembly. A member advised handing the TV to an RTV service point. This approach avoids damage when accessing the lighting strips under the matrix. [Elektroda, Pedros050, post #17162405]

How much does replacing LED backlight strips cost?

There is no fixed price. As one technician noted, “each website counts differently,” so ask local service centers for quotes. Expect variability by region and parts used. [Elektroda, Pedros050, post #17162446]

What do the LED strips look like and where are they?

They are linear bars under the LCD matrix. A photo in the thread shows the strips after removing the panel layers. Access requires careful disassembly on a flat surface. [Elektroda, Pedros050, post #17162446]

What settings should I change after backlight repair?

Lower the backlight level in the Picture menu. A member reported previous settings at 100% power, and advised reducing it to improve longevity. This reduces thermal stress on new strips. [Elektroda, itadek, post #17162430]

I replaced the power supply board and still have no backlight—why?

A used, “seemingly functional” power board did not restore LED voltage in the reported case. That points to failed LED strips instead of a PSU fault. Diagnose strips before buying more boards. [Elektroda, kar-bau-kopec, post #17162278]

Will I always see backlight voltage when the TV powers on?

No. In the case discussed, the LED output showed about 60 V at startup, then dropped to 0 V. That behavior indicates a fault and prevents steady illumination. Measure at power-on to catch this brief event. [Elektroda, kar-bau-kopec, post #17162388]

Is there a step-by-step to check this backlight issue?

Try this quick flow:
  1. Do the flashlight test to confirm the image appears.
  2. Measure LED connector voltage right at power-on.
  3. If voltage is missing or collapses, suspect failed LED strips and plan replacement. [Elektroda, kar-bau-kopec, post #17162278]

Is there a repair video for the same model?

Yes. A forum member linked a repair video for this exact TV model and warned to avoid common mistakes. Watch before attempting disassembly. [Elektroda, E8600, post #17162734]
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