Emerson CLC 401EM2F 40" LCD backlight turns off after 2 seconds.

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  • paulstef
    Badcaps Veteran
    • Dec 2013
    • 724
    • Canada
    #1

    Emerson CLC 401EM2F 40" LCD backlight turns off after 2 seconds.

    Hi ,

    the TV turns on but after 2 seconds or so the backlight turns off.

    All voltages from the PS seem to be ok.

    The High voltages transformers on the inverter PCB are ok.

    My question is what exactly do I have to expect on the signal lines PWM SEL, BL ADJ and BL SW?

    BL SW is 2.95V when turning on the TV, and it stays there, BL ADJ goes to about 1.3V and then increases to 2.2V 2 seconds AFTER the backlight turns off.
    PWM SEL is at DC 1.56V while the backlight is on and then after the backlight is off has a 150Hz 3.3V signal on it.

    I assume BL SW would be "backlight switch", BL ADJ would be the intensity of the backlight . What is PWM SEL for?

    Thanks
    Attached Files
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    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA
      #2
      Re: Emerson CLC 401EM2F 40" LCD backlight turns off after 2 seconds.

      This is I assume: PWM_SEL is for, if used, PWM DIMMING CONTROL, the signal will be around 200Hz with variable pulse width from 10% (min brightness) to 90% for max brightness. BL_ADJ is an analog (variable DC) from <1V for MIN, >4V for max.
      If you can look up the LCD panel model number then you can get the spec which will tell you the electrical spec of the inverter board and the T-CON board.
      Sounds like the inverter is getting the correct signals but there is problem due to circuits or bad lamps, bad lamp wiring.
      Last edited by budm; 07-25-2014, 08:54 PM.
      Never stop learning
      Basic LCD TV and Monitor troubleshooting guides.
      http://www.badcaps.net/forum/showthr...956#post305956

      Voltage Regulator (LDO) testing:
      http://www.badcaps.net/forum/showthr...999#post300999

      Inverter testing using old CFL:
      http://www.badcaps.net/forum/showthr...er+testing+cfl

      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
      http://s807.photobucket.com/user/budm/library/

      TV Factory reset codes listing:
      http://www.badcaps.net/forum/showthread.php?t=24809

        Comment

        • paulstef
          Badcaps Veteran
          • Dec 2013
          • 724
          • Canada
          #3
          Re: Emerson CLC 401EM2F 40" LCD backlight turns off after 2 seconds.

          Ok, thanks. I will check the panel tomorrow.

          What voltages can I expect on the secondary of the inverter transformers? I could borrow a high voltage probe next week.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA
              #4
              Re: Emerson CLC 401EM2F 40" LCD backlight turns off after 2 seconds.

              1500~2000V!
              I use this to test each output to see if one of them is bad:
              https://www.badcaps.net/forum/showth...x+dx-40l261a12
              Never stop learning
              Basic LCD TV and Monitor troubleshooting guides.
              http://www.badcaps.net/forum/showthr...956#post305956

              Voltage Regulator (LDO) testing:
              http://www.badcaps.net/forum/showthr...999#post300999

              Inverter testing using old CFL:
              http://www.badcaps.net/forum/showthr...er+testing+cfl

              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
              http://s807.photobucket.com/user/budm/library/

              TV Factory reset codes listing:
              http://www.badcaps.net/forum/showthread.php?t=24809

                Comment

                • paulstef
                  Badcaps Veteran
                  • Dec 2013
                  • 724
                  • Canada
                  #5
                  Re: Emerson CLC 401EM2F 40" LCD backlight turns off after 2 seconds.

                  Bdm , I think you brought me on the right track .

                  Apart from lcdparts.net, is there any other reliable store to buy HV transformers? They don't seem to have it. Otherwise I would need a new inverter board...
                  Attached Files

                    Comment

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