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

Telo 64518 31
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  • #1 19067999
    Telo
    Service technician RTV  
    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%.
    Attachments:
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  • #2 19068066
    kazikszach
    Level 38  
    You have slats to replace, these new LG TVs probably have it, I had several cases.
  • #3 19068068
    Dorian Olech
    Level 29  
    Remove the matrix and see how the slats shine. 90% of them are replaceable.
  • #4 19068131
    Telo
    Service technician RTV  
    Thank you for the quick response, tomorrow I will dismantle the matrix and turn it on.
    I guessed so.
  • #5 19068139
    kazikszach
    Level 38  
    And of course, after replacing the backlight, set it to 60%.
  • #6 19068185
    GanCegall
    Level 38  
    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  
    The current must be adjusted by the PWM controller.

    From the user menu the customer can always adjust.
  • #8 19185466
    Telo
    Service technician RTV  
    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.
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  • #9 19185948
    Adewag
    Level 21  
    Service remote and backlight level change from 100% to lower. Less chance that the customer will change something, as in a regular menu.
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  • #10 19186002
    badael
    Level 26  
    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  
    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  
    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  
    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  
    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  
    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  
    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.
  • #17 19188626
    Adewag
    Level 21  
    jeloi wrote:
    Combined Korean aluminum-based diodes is the best solution.


    Has anyone installed these strips?
  • #18 19191761
    Telo
    Service technician RTV  
    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?
  • #20 19191992
    Dorian Olech
    Level 29  
    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  
    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  
    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  
    An oscilloscope would be better, but I don't have access to this TV model at the moment.
  • #24 19194583
    Telo
    Service technician RTV  
    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 26  
    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  
    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  
    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?
    Attachments:
  • #28 19197619
    badael
    Level 26  
    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  
    >>19068185
    How many strips are in this TV, 3 pcs?
  • #30 20472191
    Telo
    Service technician RTV  
    Yes, 3 pcs are installed
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Topic summary

The discussion revolves around the LG 43UJ6517 television model, which exhibits a blue shade dominance in its picture quality, particularly on the left side. Users suggest that the issue is likely due to faulty LED backlight strips, which may need replacement. Several participants recommend checking the LED strips' performance after disassembly and adjusting the backlight settings to prevent excessive brightness. The conversation also touches on the importance of current control in the power supply and the potential need to change current control resistors to enhance LED longevity. The original LED strips are discussed in terms of quality, with a preference for Korean components over cheaper alternatives. Measurements of current and voltage adjustments are shared, indicating the complexity of the backlight system in this model.
Summary generated by the language model.
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