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Samsung UE55MU6120K Boot loop with backlight no video

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  • Davi.p
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Diarrhea don't bother me ok? So now you must keep a lesson on why this is dangerous.. we listen..

    Leave a comment:


  • Diah
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by lotas View Post
    Do not try to supply 12v anywhere, otherwise you will completely kill your panel and motherboard! Check with a multimeter for resistance these leads on the protective diode assemblies relative to gnd.
    +10

    Originally posted by Davi.p View Post
    inject 12v on the 15v line, prepare to remove it when you see something wrong, better if you increase current slowly..
    could you please stop this stupid suggestion..

    as Lotas said ESD diode... but if one shorted.. you will have cell shorted.. the solution block all ckv from the top LVDS socket at MB side. other wise this is rubbish Panel.

    Leave a comment:


  • lotas
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Do not try to supply 12v anywhere, otherwise you will completely kill your panel and motherboard! Check with a multimeter for resistance these leads on the protective diode assemblies relative to gnd.
    Attached Files

    Leave a comment:


  • fanaticgames
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by Davi.p View Post
    Ah, yes, try switching normally on the tv, if you can locate a 15 v for a short time on the capacitors on the screen's boards then you have located the 15v on those condensers, if the voltages does not appear then you must search for technical document of the model, or study the circuit on mainbboard , if you can't i need very sharp picture of it.
    Left and right board photo:
    Attached Files

    Leave a comment:


  • Davi.p
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Ah, yes, try switching normally on the tv, if you can locate a 15 v for a short time on the capacitors on the screen's boards then you have located the 15v on those condensers, if the voltages does not appear then you must search for technical document of the model, or study the circuit on mainbboard , if you can't i need very sharp picture of it.

    Leave a comment:


  • fanaticgames
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by Davi.p View Post
    inject 12v on the 15v line, prepare to remove it when you see something wrong, better if you increase current slowly..

    are we talking about giving current to the panel? and where I find the 15v line I have no diagrams and nothing is indicated on the pcb

    Leave a comment:


  • Davi.p
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    inject 12v on the 15v line, prepare to remove it when you see something wrong, better if you increase current slowly..

    Leave a comment:


  • fanaticgames
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by Davi.p View Post
    locate on the panel connector if it is present a 1,8/3,3v
    yes I checked the winbond chip on the left pcb and there is 3.3V

    I did some random tests with tape on the panel flats and the TV doesn't restart anymore and you can hear the audio and the backlight works but the screen is completely black, no image

    Leave a comment:


  • Davi.p
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    locate on the panel connector if it is present a 1,8/3,3v

    Leave a comment:


  • fanaticgames
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by Davi.p View Post
    yep
    Nope, I didn't find any shorted capacitors

    Leave a comment:


  • Davi.p
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    yep

    Leave a comment:


  • fanaticgames
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by Davi.p View Post
    ok so panel problem mostly, check on the screen's small large boards if there's a short on the caps
    do you mean on the two pcb right and left in the panel?
    Last edited by fanaticgames; 02-18-2023, 10:26 AM.

    Leave a comment:


  • fanaticgames
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by zwarder View Post
    try blocking ckv lines, worked for me

    I can't identify the ckv lines on this model, can you help me?

    I can't connect the tracks to the serigraphs
    Attached Files
    Last edited by fanaticgames; 02-18-2023, 10:44 AM.

    Leave a comment:


  • zwarder
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    try blocking ckv lines, worked for me

    Leave a comment:


  • Davi.p
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    ok so panel problem mostly, check on the screen's small large boards if there's a short on the caps

    Leave a comment:


  • fanaticgames
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by Davi.p View Post
    meta?? Half, che meta?? :+)

    1) how can you state that tv is boot looping? Backlight does on-off?
    2) so detaching a flat b.l. stays on?
    Sorry, yes half display :-)

    1) yes, the backlight turns on and off because the tv restarts, you can tell by the red status led

    2) if I disconnect the 12 pin cable that goes to the motherboard the backlight stays on without problems

    Leave a comment:


  • fanaticgames
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by KYBOSH View Post
    Its either the mainboard... or display as you have surmised.

    The 'easiest' way to determine which is which for certain is to get a verified good replacement mainboard and install it. if the TV works then its the mainboard.
    The key here is to get a mainboard that is VERIFIED good.

    Some of the ones you see on eBay cant be verified bcos they were pulled from TVs with damaged screens that actually never displayed a picture. The issue with those boards could be the screen, the mainboard or both. The seller will almost never verify the part before selling and just assume its good.

    The harder way is to test voltages on the mainboard while in a sort of diagnostic mode. This is where you trick the mainboard to think it has a good display attached and it sends signals it normally would. Different mainboards have different ways to initiate this diagnostic test. Some are as easy as putting a jumper on easily accessible pins. Others require soldering different traces together.


    But before you do this you may want to check your backlights. Often times they are 'kind of' bad. Good enough to light up but bad enough to trip a protection circuit on the mainboard.
    You'd do this with a backlight tester but it 'may' require you to open up the panel and remove the display screen to get access to them.

    Good luck
    if I unplug the cable between the motherboard and the power supply, the LEDs stay on without problems even for 15 minutes, if they were faulty they didn't light up at all or not?

    my question is if I test it with scotch tape by eliminating some clock signal lines, can I figure out if it's a display or motherboard problem?
    Last edited by fanaticgames; 02-05-2023, 02:58 PM.

    Leave a comment:


  • fanaticgames
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Originally posted by nomoresonys View Post
    not understanding, what exactly are the symptoms?
    the tv turns on, the screen stays black with the backlight on and restarts continuously after 3 seconds. If I remove the panel flats, the TV turns on regularly, I hear sounds, the remote control responds and everything seems to work

    Leave a comment:


  • Davi.p
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    meta?? Half, che meta?? :+)

    1) how can you state that tv is boot looping? Backlight does on-off?
    2) so detaching a flat b.l. stays on?

    Leave a comment:


  • KYBOSH
    replied
    Re: Samsung UE55MU6120K Boot loop with backlight no video

    Its either the mainboard... or display as you have surmised.

    The 'easiest' way to determine which is which for certain is to get a verified good replacement mainboard and install it. if the TV works then its the mainboard.
    The key here is to get a mainboard that is VERIFIED good.

    Some of the ones you see on eBay cant be verified bcos they were pulled from TVs with damaged screens that actually never displayed a picture. The issue with those boards could be the screen, the mainboard or both. The seller will almost never verify the part before selling and just assume its good.

    The harder way is to test voltages on the mainboard while in a sort of diagnostic mode. This is where you trick the mainboard to think it has a good display attached and it sends signals it normally would. Different mainboards have different ways to initiate this diagnostic test. Some are as easy as putting a jumper on easily accessible pins. Others require soldering different traces together.


    But before you do this you may want to check your backlights. Often times they are 'kind of' bad. Good enough to light up but bad enough to trip a protection circuit on the mainboard.
    You'd do this with a backlight tester but it 'may' require you to open up the panel and remove the display screen to get access to them.

    Good luck

    Leave a comment:

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