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Plasma, Philips 42PF7520D.10 LC4.9E/ab Chassis

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    Plasma, Philips 42PF7520D.10 LC4.9E/ab Chassis

    This set was originally dead, apart from the green light which would cycle on/off every 10-15 seconds or so.

    That fault was a surface-mount cap, C2508 in the PSU board. Many other of those 'Orrible surface-mount electrolytics have also been replaced in an attempt to cure the other fault.

    That other fault--which it still has occurs when the set is cold. Certain brightness parts of a picture will be very 'noisy' sparklies/greenish/black usually following lines of contour, say a person's face, you get hideous 'lines' almost making the picture look negative--but its not...

    As the set warms up, this lessens to Almost un-noticable, almost perfect, but the certain brightness still has a 'shimmer' There's a few sparklies of green/red on black of the pic..

    Bright scenes are good, bright, sharp. no signs of streaking or picture retention etc.

    The PSU voltages are all correct but there's one supply, 'Vw' checkable on YSUS thats about 8-9V higher than it should be. (186V)

    --There Are NO Presets/adjustments In The PSU or the YSUS. Only one pot in the XSUS--that has no effect on anything -it seems, Ive had most of the boards out and checked, replaced the odd cap here and there to no avail.

    Looking at the manual suggests its all set in software, but makes no mention of how to alter the PSU rails.
    The voltage stays the same during fault and when the set is near perfect after warming up.....

    Any ideas....?
    TELEFIX

    How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
    http://www.irf.com/technical-info/appnotes/an-1088.pdf
    PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

    #2
    Re: Plasma, Philips 42PF7520D.10 LC4.9E/ab Chassis

    I have had this problem too.

    I don't know how to fix it as I've always managed it by adjusting the brightness and contrast.

    However, I do know the adjustments are made on the VRS and VRA lines; so if you could find some way to change these you may be able to fix the problem.
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

    Comment


      #3
      Re: Plasma, Philips 42PF7520D.10 LC4.9E/ab Chassis

      Ah--Cheers Tom, --Now to sound like a complete numpty--What are the VRS/VRA lines--summit to do with I2Cbus control?

      (Used to be video/TV tech for many years, but only just getting into all this flat-screen stuff!)

      Does this fault get worse in the short term do you know?--Your answer suggests not. I planned to give the set--if working reasonably--to the Mother-In Law!
      TELEFIX

      How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
      http://www.irf.com/technical-info/appnotes/an-1088.pdf
      PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

      Comment


        #4
        Re: Plasma, Philips 42PF7520D.10 LC4.9E/ab Chassis

        They are voltages -- they control the SMPS output by some gain factor.
        It seems to get worse then stop, though mine only had slightly dark speckles on some scenes.
        Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
        For service manual, schematic, boardview (board view), datasheet, cad - use our search.

        Comment


          #5
          Re: Plasma, Philips 42PF7520D.10 LC4.9E/ab Chassis

          Ah right, I see! Typical Philips!

          I did think of trying the 'Load default values in NVM' as indicated in the manual--But thought better of it....
          Knowing my luck, I would 'Brick' the thing!

          Thanks for your help.
          TELEFIX

          How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
          http://www.irf.com/technical-info/appnotes/an-1088.pdf
          PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

          Comment

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