Lenovo G555, only external display working

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  • ktmmotocross
    Boardkiller
    • Feb 2014
    • 3553
    • slovakia

    #1

    Lenovo G555, only external display working

    Hello. Have this lenovo g555 with ATI igp. problem is that it display only on external. i replace aTI IGP with new working one but nothing changed.

    lid sw have power. it is UMA version
  • alihomee
    Badcaps Legend
    • Dec 2012
    • 1565
    • malaysia

    #2
    Re: Lenovo G555, only external display working

    check lcd cable or ur screen

    Comment

    • ktmmotocross
      Boardkiller
      • Feb 2014
      • 3553
      • slovakia

      #3
      Re: Lenovo G555, only external display working

      cable checked, lcd changed

      Comment

      • Life Goes On
        Badcaps Veteran
        • May 2014
        • 264
        • Curacao

        #4
        Re: Lenovo G555, only external display working

        Check the connector from the cable.
        The Night Drop Down, I Will Keep Try Until..., You Never know.
        Dushi Kòrsou, Nos Tei.

        Comment

        • samanthban
          Badcaps Veteran
          • Feb 2014
          • 253
          • Sri lanka

          #5
          Re: Lenovo G555, only external display working

          please post here if you have the schematic.
          sigpic

          Comment

          • ktmmotocross
            Boardkiller
            • Feb 2014
            • 3553
            • slovakia

            #6
            Re: Lenovo G555, only external display working

            here is schematic
            Attached Files
            Last edited by ktmmotocross; 06-28-2015, 12:52 AM.

            Comment

            • atsio
              Badcaps Veteran
              • Oct 2013
              • 819
              • Greece

              #7
              Re: Lenovo G555, only external display working

              Please post voltages on lvds connector.

              Comment

              • ktmmotocross
                Boardkiller
                • Feb 2014
                • 3553
                • slovakia

                #8
                Re: Lenovo G555, only external display working

                here is measurements of lvds connector
                Attached Files

                Comment

                • atsio
                  Badcaps Veteran
                  • Oct 2013
                  • 819
                  • Greece

                  #9
                  Re: Lenovo G555, only external display working

                  You seem to have a problem with KBC. Try to inject 3.3v on the dac_brig pin.

                  Comment

                  • ktmmotocross
                    Boardkiller
                    • Feb 2014
                    • 3553
                    • slovakia

                    #10
                    Re: Lenovo G555, only external display working

                    i just replaced kbc but nothing changed. try to inject. what is dac_brig signal for?

                    Comment

                    • ktmmotocross
                      Boardkiller
                      • Feb 2014
                      • 3553
                      • slovakia

                      #11
                      Re: Lenovo G555, only external display working

                      inject 3.3V but no change

                      Comment

                      • atsio
                        Badcaps Veteran
                        • Oct 2013
                        • 819
                        • Greece

                        #12
                        Re: Lenovo G555, only external display working

                        brightness. Probably no enbkl signal.

                        Comment

                        • atsio
                          Badcaps Veteran
                          • Oct 2013
                          • 819
                          • Greece

                          #13
                          Re: Lenovo G555, only external display working

                          Measure the signals on the screens lvds connector

                          Comment

                          • ktmmotocross
                            Boardkiller
                            • Feb 2014
                            • 3553
                            • slovakia

                            #14
                            Re: Lenovo G555, only external display working

                            rightness is regulated from UMA_PWM. ENBL signal is for VGA

                            Comment

                            • atsio
                              Badcaps Veteran
                              • Oct 2013
                              • 819
                              • Greece

                              #15
                              Re: Lenovo G555, only external display working

                              I just noticed that you have an 15.6 ccfl screen (although schematic mentions led)

                              From an inverter datasheet:

                              "
                              There are two control signals that come form syst
                              em to control lamp brightness. One signal is
                              named DAC_BRIG, which limits curr
                              ent to meet LCD lamp current specification. Another one is
                              named PWM, which adjusts lamp br
                              ightness. This invert
                              er brightness is adjusted by PWM burst
                              mode. The PWM burst mode is that turning on and
                              off the lamp at rate of 150Hz. The effective
                              brightness is a function of the duty cycle.

                              "

                              ENBKL signal is raised from Northbridge and goes to KBC

                              Comment

                              • ktmmotocross
                                Boardkiller
                                • Feb 2014
                                • 3553
                                • slovakia

                                #16
                                Re: Lenovo G555, only external display working

                                but i dont have problem with backlight. i have problem with no lcd daa. i can turn on backlight but still no data or bad data

                                Comment

                                • ktmmotocross
                                  Boardkiller
                                  • Feb 2014
                                  • 3553
                                  • slovakia

                                  #17
                                  Re: Lenovo G555, only external display working

                                  flashed bios, no change

                                  for me it looks like bad clock signal or something like that. the image is distorted but i see that is something displaying but its lines

                                  Comment

                                  • atsio
                                    Badcaps Veteran
                                    • Oct 2013
                                    • 819
                                    • Greece

                                    #18
                                    Re: Lenovo G555, only external display working

                                    You have to remove Northbridge and check lines to lvds connector

                                    Comment

                                    • ktmmotocross
                                      Boardkiller
                                      • Feb 2014
                                      • 3553
                                      • slovakia

                                      #19
                                      Re: Lenovo G555, only external display working

                                      Ilast time i have sb off the board i checked these connections and it was al good.
                                      What is lcd clock frequency? Now dont have scope to chrck it.

                                      Comment

                                      • atsio
                                        Badcaps Veteran
                                        • Oct 2013
                                        • 819
                                        • Greece

                                        #20
                                        Re: Lenovo G555, only external display working

                                        What is SB has to do with GMCH_TX*** lines?

                                        Comment

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