LG 42LK450 will not turn on

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  • Ltank
    Badcaps Veteran
    • Jun 2013
    • 776
    • USA
    #1

    LG 42LK450 will not turn on

    P.S. has 3.5vdc stby. Will not turn on. I can make the P.S. turn on by jumping
    3.5vdc to PWR_On, 3.5vdc to Inv-On and 3.5vdc to A-Dim. the backlights turn on and stay on. with everything connected. the 3.vdc is there but the set is dead. No command to the P.S. on pin#1 to turn on the supply.
    The Service manual trouble shooting guide says to reload Micom software or to replace Micom (IC1002) or main board. My major question is this. If the set will not turn on and there is no video, How do I install the new Micom software and where can I get it?
    Tags: None
    • Ltank
      Badcaps Veteran
      • Jun 2013
      • 776
      • USA
      #2
      Re: LG 42LK450 will not turn on

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        • aaronwt6
          Badcaps Veteran
          • Apr 2013
          • 855
          • US
          #3
          Re: LG 42LK450 will not turn on

          I've replaced 3 of those main boards. Two in the 55" version, and another just like yours. They are crap as far as I can tell. As far as the firmware, the only way you could re-do it would be to replace the eeprom chip. I'm doubting it would help though. Mine had numerous failed voltage regulators.

            Comment

            • Ltank
              Badcaps Veteran
              • Jun 2013
              • 776
              • USA
              #4
              Re: LG 42LK450 will not turn on

              This one only has 3.5vdc from PS. it does not send PS-On command to turn PS on to send the 12vdc and 24vdc back to the boards voltage regulators. There were not shorted.

                Comment

                • Ltank
                  Badcaps Veteran
                  • Jun 2013
                  • 776
                  • USA
                  #5
                  Re: LG 42LK450 will not turn on

                  Customer said problem was backlight flickers then set shuts off. When I tested it. I got a different problem the set would not turn on. Main board was bad. Got a second main board and it turns on but backlight flickers now back the customers original complaint. The Inverter on is stable as is the 24vdc to the inverter. The A-Dim command to the powersupply is 8vdc. There is an Error voltage on PS pin#24. I can disconnect the wires from the connector
                  P201 for the pin#24 and or the #18 A-Dim and the backlight still flickers.
                  The PS 24vdc is solid 23.95 with very small changes. I can jumper the PS on and the backlight is steady. Another bad PS? What am I missing?

                    Comment

                    • Ltank
                      Badcaps Veteran
                      • Jun 2013
                      • 776
                      • USA
                      #6
                      Re: LG 42LK450 will not turn on

                      The PS has 8 vdc on the A-dim on the PS with the wire disconnected from P201 on the PS. As previously stated jumpering the PS the backlight does not flicker. Connecting the MB to the PS the backlight flickers then shuts down. The Backlight turns off first then the MB turns of the PS on comand. Bad MB? Again?

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