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Thread: Help with Interference on RGB osd mux Lg 20” cp-20b85

  1. #1
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    Help with Interference on RGB osd mux Lg 20” cp-20b85

    Hello Guys
    With the help of a very good friend Mark from Australia, i was able to mod a Lg 20” cp-20b85 Rgb osd mux the chassi is MC-83a, the process was perfect except with a noise with a "S" dancing pattern that is occuring specialy with solid background, below is the album with the instalation and examples with that interference.

    Will try to describe the walkthru that Mark and i did on this chassi:
    a) This mod was intend to run with a pc with an ATI-5450 (patched with 15khz) and CRt_Emudriver 2.0 beta 10 on windows 7
    b) took of the RF modulator to avoid any future interference, and on that spot solder GNG (pin 10) from vga
    c) Used the 5v from RF to feed R50 to trigger the FB
    d) Sync did the twist on pins 13 and 14 with 1k in each them twisted togheter and run it on AV central pin
    e) bring colours from VGA direct in a 75ohms already exist spot in chassi near rgb resistor (220ohs) on chassi.

    To try to show Mark the interference with a very good way not only as a "ghost" on background i put a pot 10k on 5v source, and when you turn it almost to make trigger disappear or oposite almost to trriger on, the real "S" dancing interference pattern show all in it΄s glory.

    Album with instalation: https://photos.app.goo.gl/Qkxyc2ptez2guZxH7

    So if anyone have some idea or a clue that we can do to try to minime or solve that interference will be extreme glad!

    OBS: I even try to put some ceramic caps (pf ones) that was supposed to be in chassi but was not, to try to minimize the interference, but unfortunely did nothing, image stays with same interference.

    Thanks a lot
    Marcos

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    > OBS: I even try to put some ceramic caps (pf ones) that was supposed to be in chassi but was not, to try to minimize the interference, but unfortunely did nothing, image stays with same interference.

    To add some extra context here, the schematic for the TV shows some small filter caps on RGB and blanking lines (maybe sync too? I forget exactly) that the factory chose not to install. Marcos installed these in the hope that they would.

    Didn't add mux resistors on this TV as it was already using 75R as the ground resistors on the OSD RGB lines.

    Marcos....Have you tried undoing the blanking and feeding regular AV footage yet?

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    Hey Mark
    Thanks a lot bud, for additional information, will definely test the AV port with regular footage thru video to check if interference persist on that way.
    Will let you know the results.

    Thanks a lot
    Marcos

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    Marcos have you been able to solve the problem of interference?

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    Bom dia Romariu
    Tudo blz !
    Infelizmente ainda nγo consegui essa interferencia, estou tentando com o Mark da Australia, mas atι agora nγo consegui retirar a interferencia.
    Tentei instalar uns capacitores minusculos (pf) no chassi que era para estar la e nγo esta, mesmo assim nada de melhorar a interferencia.
    Caso se consiga por ai tambιm me da um tok!

    Vlw abs
    Marcos

  6. #6
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    Bom dia tambem Marcos obrigado por responder ainda estou na luta de tentar tirar essa interferencia e nada mas qualquer coisa te dou um tok.
    Inclusive ja tentei em uma outra muito semelhante a essa LG CP-20K40 e aconteceu a mesma coisa.


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