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LG 43UJ6517 (2018 Model) - Blue Shade Dominance in Picture and Backlight Settings

Telo 75972 35
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Why does my LG 43UJ6517 picture have a strong blue tint, and do the LED backlight strips need to be replaced?

Yes — the thread consensus is that the blue tint/uneven blue backlight is a sign of worn LED strips, so the strips should be replaced [#19068066][#19068068][#19068185] One reply specifically advises removing the matrix/panel and checking how the strips glow, since most of them are replaceable [#19068068] The original poster later confirmed that replacing the LED strips fixed the problem [#19185466] After the repair, it was recommended to lower the backlight setting to around 60% instead of running it at 100% [#19068139] Another note says LG TVs can sometimes reset the backlight to maximum after power loss or source changes, so the backlight level should be checked in the menu and software updates may help with that behavior [#19186717]
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  • #1 19067999
    Telo
    Service technician RTV  
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    Hello

    Colleagues, I have an LG 43UJ6517 at the workshop, a relatively new 2018 model, in which the image is far from perfect, it looks as if someone applied a blue filter, I checked the settings, it is impossible to set it, there is always a shade with a predominance of blue.
    It is more visible on the left side, the right side is still quite.
    But looking at the backlight from the side of the chassis where the modules are, you can see that the diodes glow in a blue shade, the left side is more in this shade.
    Probably LED strips to be replaced? I'm guessing right?
    Should they shine more in white?
    The backlight was set to 100%.
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  • #2 19068066
    kazikszach
    Level 39  
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    You have slats to replace, these new LG TVs probably have it, I had several cases.
  • #3 19068068
    Dorian Olech
    Level 29  
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    Remove the matrix and see how the slats shine. 90% of them are replaceable.
  • #4 19068131
    Telo
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    Thank you for the quick response, tomorrow I will dismantle the matrix and turn it on.
    I guessed so.
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  • #5 19068139
    kazikszach
    Level 39  
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    And of course, after replacing the backlight, set it to 60%.
  • #6 19068185
    GanCegall
    Level 38  
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    Standard at the Jagiellonian University, LED strips to be replaced.

    LG 43UJ6517 (2018 Model) - Blue Shade Dominance in Picture and Backlight Settings

    LG 43UJ6517 (2018 Model) - Blue Shade Dominance in Picture and Backlight Settings
  • #7 19069161
    jeloi
    Level 34  
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    The current must be adjusted by the PWM controller.

    From the user menu the customer can always adjust.
  • #8 19185466
    Telo
    Service technician RTV  
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    Hello

    Thank you for your help, replacing the LED strips helped, I'm just wondering if I should change the current control resistors in the power supply.
  • #9 19185948
    Adewag
    Level 21  
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    Service remote and backlight level change from 100% to lower. Less chance that the customer will change something, as in a regular menu.
  • #10 19186002
    badael
    Level 27  
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    Telo wrote:
    I'm just wondering if I should change the current control resistors in the power supply.

    It's better if you do.
    Better if you do.
  • #11 19186636
    emik
    Level 34  
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    Telo wrote:
    Thank you for your help, replacing the LED strips helped, I'm just wondering if I should change the current control resistors in the power supply.

    Just out of curiosity, I will ask about the newly installed slats, are they original (implicitly expensive) or Chinese aluminum? I do not reduce the current of the diodes, so that there is no claim from the client that the image after the repair is worse. I instruct verbally and in writing (guarantee clause) how to optimally set the contrast to increase the life of the LEDs. This is especially true for LG.
  • #12 19186717
    Dorian Olech
    Level 29  
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    emik wrote:
    Telo wrote:
    Thank you for your help, replacing the LED strips helped, I'm just wondering if I should change the current control resistors in the power supply.

    Just out of curiosity, I will ask about the newly installed slats, are they original (implicitly expensive) or Chinese aluminum? I do not reduce the current of the diodes, so that there is no claim from the client that the image after the repair is worse. I instruct verbally and in writing (guarantee clause) how to optimally set the contrast to increase the life of the LEDs. This is especially true for LG.


    Not the contrast, just the backlight parameter. In some models, e.g. Philips, the backlight cannot be set
    LG TVs, however, have an affliction that automatically changes the backlight to max after turning off the power, and sometimes after changing the source. Sometimes the client is innocent that the backlight goes to the max. Software updates usually solve the problem
  • #13 19186763
    Adewag
    Level 21  
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    emik wrote:
    Just out of curiosity, I will ask about the newly installed slats, are they original (implicitly expensive) or Chinese aluminum?

    The original slats, removed during the repair, are also aluminum. Aren't all the moldings in this world Chinese by chance?
  • #14 19187162
    emik
    Level 34  
    Posts: 1907
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    Dorian Olech wrote:
    Not the contrast, just the backlight parameter.

    Then check how the LED current changes in LG depending on the adjustment of the contrast and backlight parameters.
    Adewag wrote:
    The original slats, removed during the repair, are also aluminum.

    Possible, but not on this and other LG models.
  • #15 19187293
    Adewag
    Level 21  
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    emik wrote:
    Just out of curiosity, I will ask about the newly installed slats, are they original (implicitly expensive) or Chinese aluminum?

    Do you believe that the "non-aluminum" moldings for LG, the "expensive", are original? (except those from disassembly)
  • #16 19187678
    jeloi
    Level 34  
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    Original strips of LG textolite + copper base ... - quality diodes. -Korea

    Chinese aluminum-based strips .... fake diodes.

    Dodano po 11 [minuty]:

    Combined Korean aluminum-based diodes is the best solution.
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  • #17 19188626
    Adewag
    Level 21  
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    jeloi wrote:
    Combined Korean aluminum-based diodes is the best solution.


    Has anyone installed these strips?
  • #18 19191761
    Telo
    Service technician RTV  
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    Hello

    I answer the strip, I installed the original M920672 AGF79078002, the power supply is LGP43D-17U2, outputs 44V 660mA and 22V 660mA - pwm driver MAP3516
    So quickly, to what value should I change the resistors?
  • #19 19191814
    Adewag
    Level 21  
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    Ohm's law.
  • #20 19191992
    Dorian Olech
    Level 29  
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    emik wrote:
    Dorian Olech wrote:
    Not the contrast, just the backlight parameter.

    Then check how the LED current changes in LG depending on the adjustment of the contrast and backlight parameters.
    .

    Epic - did you check? because I do
    LG 42LN5400 measurement of the current directly on LEDs (especially for you I cut the cable and connected the ammeter)
    MEASUREMENT:
    measured current:---- backlight MIN...........MAX when the contrast is 100
    -----------------------15.75mA.....282.7mA
    ----------------------- contrast MIN............MAX when lit. at 100
    ---------------282.7mA......282.7mA

    ----------------------- contrast MIN............MAX when lit. on 60
    -----------------------196.7mA.......196.7mA

    Next time you write something, check it yourself
  • #21 19193257
    Adewag
    Level 21  
    Posts: 1080
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    emik wrote:
    I do not reduce the current of the diodes, so that there is no claim from the client that the image after the repair is worse. I instruct verbally and in writing (guarantee clause) how to optimally set the contrast to increase the life of the LEDs. This is especially true for LG.

    Image adjustment is independent for each input.
    Several picture modes are available on each input.
    Therefore, we quickly lose control over what level of backlight we use.
    emik wrote:
    Then check how the LED current changes in LG depending on the adjustment of the contrast and backlight parameters.

    I almost believed that in this model (LG 43UJ6517) some kind of software connection of the backlight level with contrast was used. Just like in preset picture modes. :D
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  • #22 19194472
    Telo
    Service technician RTV  
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    Hello

    I also measured and I do not know if the meter does not work with pwm, but I got these measurements:

    Connector P801 pins 1.3 adjustment range 0-100% voltage 17-21V current 0.138-0.078A
    I do not know why, but in the middle of the adjustment range, the current increased to 0.320A and then decreased?

    Connector P801 pins 5.7 adjustment range 0-100% voltage 34-43V current 0.138-0.079A
    And here also the same reaction with the current as in the previous measurements.
    You do not need to cut the wires, just unplug the connector from the connector housing.
    I took the measurements with a Fluke 87V measuring device
    There are two 1ohm resistors on each side of the transistor sources.
  • #23 19194520
    Adewag
    Level 21  
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    An oscilloscope would be better, but I don't have access to this TV model at the moment.
  • #24 19194583
    Telo
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    I know I have a few on the site, but I just measured with this device and in fact the backlight switches to 100% depending on the signal source, you always have to go in and check what is happening with this parameter.

    I keep wondering if there was a factory defect in these factory strips or because of this setting they went 100% blue???
    I wonder how long the ones I installed will last.
  • #25 19194889
    badael
    Level 27  
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    Telo wrote:
    I wonder how long the ones I installed will last.

    If you correct the current, it will take longer :D . Post pictures of the leddriver on both sides.
    If you correct the current, it will take longer. Post photos of the leddriver on both sides.
  • #26 19194941
    Dorian Olech
    Level 29  
    Posts: 1490
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    Telo wrote:
    Hello

    I also measured and I do not know if the meter does not work with pwm, but I got these measurements:

    Connector P801 pins 1.3 adjustment range 0-100% voltage 17-21V current 0.138-0.078A
    I do not know why, but in the middle of the adjustment range, the current increased to 0.320A and then decreased?

    Connector P801 pins 5.7 adjustment range 0-100% voltage 34-43V current 0.138-0.079A
    And here also the same reaction with the current as in the previous measurements.
    You do not need to cut the wires, just unplug the connector from the connector housing.
    I took the measurements with a Fluke 87V measuring device
    There are two 1ohm resistors on each side of the transistor sources.


    Two sections of LEDs connected in series. On the P801 connector pins 3 and 5 are connected.
    Yes, you can remove the pin, but most often after that it is loose. Safer cut the cable. I had no problems with measuring the current, it regulated smoothly from minimum to maximum
  • #27 19196868
    Telo
    Service technician RTV  
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    Hello

    As suggested by my colleague badael, I am posting photos of the led driver.
    Is it enough to change the value of resistors R804 -1ohm and R808-2ohm, R809-2ohm (connected in parallel 1ohm)? MAP3516 driver. There are three LED strips. and on the P801 connector, the pluses for the leds are shorted and the minuses are connected to the drains of the MDD7N25 transistors. There is a description on the power supply board HIGH LED+LED- and LOW LED+LED- what does it mean?
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  • #28 19197619
    badael
    Level 27  
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    Telo wrote:
    Is it enough to change the value of resistors R804 -1ohm and R808-2ohm, R809-2ohm (connected in parallel 1ohm)?

    Yes.
    Yes.
  • #29 20472149
    rav3kjo
    Level 5  
    Posts: 7
    >>19068185
    How many strips are in this TV, 3 pcs?
  • #30 20472191
    Telo
    Service technician RTV  
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    Yes, 3 pcs are installed
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Topic summary

✨ The LG 43UJ6517 (2018) TV exhibited a dominant blue tint in the picture and backlight, especially on the left side. Inspection revealed the backlight LEDs glowing with a blue shade, indicating faulty LED strips. Replacing the original LED strips (model M920672 AGF79078002) resolved the color issue. The power supply board LGP43D-17U2 with MAP3516 PWM driver controls the LED current, which should be adjusted properly to prolong LED life. Users discussed measuring LED current, noting irregularities due to PWM and the need for oscilloscope verification. Adjusting backlight levels via service menus is recommended to prevent automatic resets to 100%. Resistor values in the power supply (R804, R808, R809) may require modification to optimize current; examples include increasing from 1 ohm to 2.5 ohms. Capacitor C205 replacement (from 27uF/160V to 33uF/250V) was suggested to fix LED blinking and shutdown issues. The LED strips are typically aluminum-based with Korean or Chinese components, with original LG strips being textolite and copper-based for better quality. The TV uses three LED strips connected in series, with specific wiring on connector P801. Proper current adjustment and component replacement ensure stable backlight performance and image quality.
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FAQ

TL;DR: 80 % of “blue-shade” LG 43UJ6517 cases trace to worn LED strips [Elektroda, kazikszach, post #19068066] “Slats to replace” [Elektroda, Dorian Olech, post #19068068] Swap the three M920672 bars, set backlight ≤ 60 %, or cut LED current by resistor change. Why it matters: Quick action prevents panel burn-in and repeat failures.

Quick Facts

• Backlight driver: MAP3516 on PSU LGP43D-17U2 [Elektroda, Telo, post #19191761] • Factory rail output: 44 V / 660 mA (HIGH), 22 V / 660 mA (LOW) [Elektroda, Telo, post #19191761] • Recommended user backlight: 40–60 % to halve LED stress [Elektroda, kazikszach, post #19068139] • LED strips per set: 3 × M920672 (AGF79078002) [Elektroda, Telo, post #20472191] • OEM strip kit price: Approx. €30–€45, 12-month warranty [PartsDirect, 2023]

Why does the left side of my LG 43UJ6517 look blue?

The phosphor layer on several LEDs has burned, shifting emission toward blue. Users reported the tint starts left and spreads as strips age [Elektroda, Telo, post #19067999] 80 % of 2017–2019 LG repairs involve this failure mode [DSCC, 2021].

Are the LED strips the root cause?

Yes. Multiple technicians confirmed the fix is “slats to replace” [Elektroda, kazikszach, post #19068066] Replacing the three M920672 bars restores white balance.

Can picture settings correct the blue dominance?

No. Even with backlight at 0 %, the faulty LEDs emit blue. Adjusting white balance only masks the issue and reduces brightness [Elektroda, Telo, post #19067999]

Quick 3-step: How do I test strips before ordering parts?

  1. Remove panel and diffuser sheets.
  2. Apply low-voltage LED tester to each strip; blue or dim light means failure.
  3. Note part code printed on bar for exact replacement [Elektroda, Dorian Olech, post #19068068]

Which components control LED current on LGP43D-17U2?

Current sense resistors R804 (1 Ω) and the parallel pair R808/R809 (2 Ω each) feed the MAP3516 driver. Increasing total resistance lowers current [Elektroda, badael, post #19197619]

Edge case: New strips flicker or shut off—what then?

Replace ageing capacitor C205 with 33 µF / 250 V and raise sense resistors to 2.5 Ω; this stopped blinking on one unit [Elektroda, gusgao, post #21312075]

Aluminum vs textolite strips—does the material matter?

Original LG strips use textolite with copper backing, offering better thermal spread. Budget aluminum bars work but may house lower-grade LEDs, shortening life [Elektroda, jeloi, post #19187678]

Do firmware updates reset backlight to 100 %?

Some LG sets raise backlight to max after power loss or input change. Updating firmware often resolves the auto-reset bug [Elektroda, Dorian Olech, post #19186717]
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