LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

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  • JDC
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally posted by budm
    This is done with the TV powered ON? You have 12V feeding the T-CON fuse F1 but the switching power supplies are dead. Based on those Voltage readings you have made the T-CON board is dead at this point.
    BTW, I hope you did the test correctly.
    I'm pretty sure I did the test correctly. I had to run my pos. probe over a file to 'sharpen" it a bit as I wasn't sure I was hitting those small areas correctly.

    In any case, I've got a TCON on its way.

    EDIT: Yes, the test was done with the TV on.

    Leave a comment:


  • budm
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally posted by JDC
    vcc = .026
    vcc18 = .025
    vgh = .022
    vgl = .050
    vdd = .018
    vcore = .022
    hvdd = .024
    This is done with the TV powered ON? You have 12V feeding the T-CON fuse F1 but the switching power supplies are dead. Based on those Voltage readings you have made the T-CON board is dead at this point.
    BTW, I hope you did the test correctly.

    Leave a comment:


  • JDC
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally posted by budm
    please check the dcv (when tv is turned on) at those test points i have marked: Black probe on the chassis.
    Vcc =
    vcc18 =
    vgh =
    vgl =
    vdd =
    vcore =
    hvdd =
    vcc = .026
    vcc18 = .025
    vgh = .022
    vgl = .050
    vdd = .018
    vcore = .022
    hvdd = .024

    Leave a comment:


  • budm
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Please check the DCV (when TV is turned ON) at those test points I have marked: Black probe on the chassis.
    VCC =
    VCC18 =
    VGH =
    VGL =
    VDD =
    VCORE =
    HVDD =
    Attached Files

    Leave a comment:


  • JDC
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally posted by dick_barton
    Yes, that is the cable.
    Awesome, thanks.

    I know what an oscilloscope looks like but have never used one. For further reference, what would the oscilloscope tell me about the LVDS cable?

    Leave a comment:


  • dick_barton
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    For clarification, the LVDS is the cable that runs from the main board to the TCON, correct?
    Yes, that is the cable.

    Leave a comment:


  • JDC
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally posted by CapLeaker
    At this point I'd really like to verify the LVDS on a oscilloscope, if there is any possibility for you to get the hands on one...
    BTW: did you already try do disconnect only one of the ribbon cables on the Tcon that go to the LCD screen, then vice versa... in order to see if there maybe half of the screen comes up?
    I did that and there was no change. As for an oscilloscope, I don't have access to one.

    For clarification, the LVDS is the cable that runs from the main board to the TCON, correct?

    Leave a comment:


  • CapLeaker
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    At this point I'd really like to verify the LVDS on a oscilloscope, if there is any possibility for you to get the hands on one...
    BTW: did you already try do disconnect only one of the ribbon cables on the Tcon that go to the LCD screen, then vice versa... in order to see if there maybe half of the screen comes up?
    Last edited by CapLeaker; 04-27-2016, 10:06 AM.

    Leave a comment:


  • JDC
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally posted by Diah
    if you put the original main board, will be easy to check after this static, by moving the load from MB step by step.

    first disconnect LVDS from MB side, and check, static remain or not, if no more you hear. then put back LVDS to MB and disconnected LVDS from T-CON and check.. still you hearing the noise mean LVDS, if static no more, go further to T-CON and so on till the ribbon cable to LCD,

    if at the first point of LVDS disconnected from MB and remain to hear static noise, then disconnect the speaker and check them of shorted. if they are well.. disconnect the IP section and check..

    this is easy way. if your measurement way you have lack or not sure of them.
    I can try that but before I do, I want to clarify what I mean by static: it's the white noise you hear when the TV isn't tuned to a good channel.

    Leave a comment:


  • JDC
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    I put the original main board in, same result except now I don't hear snow from the speakers.

    This has to be a bad TCON board.

    Leave a comment:


  • JDC
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally Posted by budm
    BTW, it took a little over 30 posts (starting at post 33) just to find out that the DCV measurement were made wrong on the T-CON board, I almost got to the breaking point, I knew it was the measurement error when it did not make any logical sense in the readings results.
    Originally posted by CapLeaker
    Wouldn't be the first time we got a run around.
    I feel bad enough, guys.

    Leave a comment:


  • CapLeaker
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally posted by budm
    BTW, it took a little over 30 posts (starting at post 33) just to find out that the DCV measurement were made wrong on the T-CON board, I almost got to the breaking point, I knew it was the measurement error when it did not make any logical sense in the readings results.
    Wouldn't be the first time we got a run around.

    Leave a comment:


  • Diah
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally posted by JDC
    I hear static (snow) when I turn it on.
    if you put the original main board, will be easy to check after this static, by moving the load from MB step by step.

    first disconnect LVDS from MB side, and check, static remain or not, if no more you hear. then put back LVDS to MB and disconnected LVDS from T-CON and check.. still you hearing the noise mean LVDS, if static no more, go further to T-CON and so on till the ribbon cable to LCD,

    if at the first point of LVDS disconnected from MB and remain to hear static noise, then disconnect the speaker and check them of shorted. if they are well.. disconnect the IP section and check..

    this is easy way. if your measurement way you have lack or not sure of them.
    Last edited by Diah; 04-27-2016, 01:25 AM.

    Leave a comment:


  • budm
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    BTW, it took a little over 30 posts (starting at post 33) just to find out that the DCV measurement were made wrong on the T-CON board, I almost got to the breaking point, I knew it was the measurement error when it did not make any logical sense in the readings results.
    Last edited by budm; 04-26-2016, 09:42 PM.

    Leave a comment:


  • CapLeaker
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Yep... change that main board out for the original one. If you have a oscilloscope handy, you could try measuring the LVDS, if the TV turns on.

    Leave a comment:


  • budm
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    At this point we know the power supply and the LED driver are working so you can leave the power supply board in place, I would put the old main board back in place and go from there.
    BTW, and no one else had worked on the TV before you received it, we hope.
    Last edited by budm; 04-26-2016, 05:21 PM.

    Leave a comment:


  • JDC
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    Originally posted by dick_barton
    I suspect Budm may be eluding to the fact that when you replaced the original fuse and had the led blinking this was probably due to the faulty led strip in the backlight.
    Once you repaired the backlights I would have expected you TV with it's original boards to be working.
    Worth a shot if I can get a hold of the original boards. I started working on this TV a month ago. I'll need to look for them.

    Leave a comment:


  • dick_barton
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    I suspect Budm may be eluding to the fact that when you replaced the original fuse and had the led blinking this was probably due to the faulty led strip in the backlight.
    Once you repaired the backlights I would have expected you TV with it's original boards to be working.
    Last edited by dick_barton; 04-26-2016, 05:12 PM.

    Leave a comment:


  • JDC
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    I think it would be best for us all if we called it a night for right now and start fresh again in a day or two. I really appreciate everyone's help and I apologize for not being more thorough. I'll do better next time, for sure.

    Leave a comment:


  • dick_barton
    replied
    Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

    As budm says it is time for a recap so we all know the next starting point.

    Leave a comment:

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