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VIZIO M557-G0: Backlights or ???

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    VIZIO M557-G0: Backlights or ???

    'Morning,
    I get sound and picture when powering on the TV and its stays that EXCEPT that the left half of the screen will dim every few seconds then return to normal while the right side of the screen performs as designed.

    Did the soft and hard reset options pulling the plug, using the reet option in the vizio menu to no avail.

    I checked the mainboard - found some popped capacitors so replaced it - but that did not change the situation.

    I checked the t-con board. It is getting good power. Then I removed one ribbon cable to see if I could isolate the problem, then the other - no impact - same situation - all backlights were lit but the left half backlights dimmed (remaining lit) then brightened and the process continued.

    The power supply board was next. The backlights are powered off this board. Checked the voltage on the connector going to the left half backlights and on two of the pins got voltage readings that read 93+ volts and then 105+ volts, rhythmic pulse voltages while the other pins reported steady voltage readings.

    Not sure where to check next. Have not jumped to taking the panels off and actually testing backlight strips - we all know that is tedious and a little tricky.

    Should I jump to that or is there something I should be check that I overlooked?

    Thank you for any insights.

    Brian

    #2
    Re: VIZIO M557-G0: Backlights or ???

    Do you have a backlight tester? I would use this first before taking it all apart. What does pulsing voltages mean? How are you measuring the voltage? Negative to chassis? Or negative to negative terminal if LEDs? We have no pictures of PSU which would be helpful and the main board with shorted caps I'm curious with pictures also what was actually replaced

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      #3
      Re: VIZIO M557-G0: Backlights or ???

      From menu go into picture settings, turn the backlights way down, see if anything changes.

      Comment


        #4
        Re: VIZIO M557-G0: Backlights or ???

        Not exactly sure but maybe checkout E900 and E902 capacitors, one may be weak.

        Comment


          #5
          Re: VIZIO M557-G0: Backlights or ???

          Originally posted by EazyBone View Post
          Do you have a backlight tester? I would use this first before taking it all apart. What does pulsing voltages mean? How are you measuring the voltage? Negative to chassis? Or negative to negative terminal if LEDs? We have no pictures of PSU which would be helpful and the main board with shorted caps I'm curious with pictures also what was actually replaced
          Thanks for replying
          It's an LED TV.

          - On backlight testing before taking apart...I measure at the pins going from the backlight connectors on the power supply board - right? PS board pic is attached and those connectors are in the upper left.

          Negative to chassis positive to pin is what I have been doing. Negative terminal ? I'm just a but confused on location.

          The main board did get completely replaced, as did the PS board. New main board also attached.

          The pulsing voltage is when I measure at the LED power supply pin connected to the PS board and hold it for a few seconds at get a reading of 93V then 105V 1-2 seconds later and then it repeats.

          Insights still appreciated
          Attached Files

          Comment


            #6
            Re: VIZIO M557-G0: Backlights or ???

            Originally posted by nomoresonys View Post
            From menu go into picture settings, turn the backlights way down, see if anything changes.
            Thanks - tried that and several other menu adjustments - no change.
            The capacitors look ok.

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