Alienware 17 R5. Does not recognise LCD...

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  • Weelcup
    TopTech
    • Oct 2017
    • 300
    • UK

    #1

    Alienware 17 R5. Does not recognise LCD...

    Hi friend.
    I have an alienware 17 R5 laptop. Which is providing LCD failure code. I have replaced the full screen unit to Full HD , QHD and 4k versions but same issue. It is just providing the LCD failure code.. which means an issue with the motherboard. It does have GTX1080 chip on board and i was wondering if the chip is causing the issue. Or might be the cpu built in intel graphic.. it is i9 cpu.
    I would be thankful if someone help me to identify the signal that is responsible for the checking the LCDfailure...

    I could not find the exact schematics of the board but this is close schematics version which belongs to 17 R4 ...
    Attached Files
  • khaahk
    Badcaps Veteran
    • Dec 2013
    • 749
    • Estonia

    #2
    Re: Alienware 17 R5. Does not recognise LCD...

    Pin 28 on edp connector might be the one. Goes to the pch.

    Comment

    • Weelcup
      TopTech
      • Oct 2017
      • 300
      • UK

      #3
      Re: Alienware 17 R5. Does not recognise LCD...

      Originally posted by khaahk
      Pin 28 on edp connector might be the one. Goes to the pch.
      Thanks for the reply.
      I will check it.

      Comment

      • Weelcup
        TopTech
        • Oct 2017
        • 300
        • UK

        #4
        Re: Alienware 17 R5. Does not recognise LCD...

        Originally posted by Weelcup
        Thanks for the reply.
        I will check it.
        Hi again
        I tried to trace the DET line but it is very hard to find it out. This because the PCH is different in the model i have . My PCH is SR40E and the one the schematic providing is SR2CE.

        However, when i connect the motherboard to external display it does not post too and provide the same error code.

        Very confusing!
        Last edited by Weelcup; 04-12-2020, 05:06 PM.

        Comment

        • khaahk
          Badcaps Veteran
          • Dec 2013
          • 749
          • Estonia

          #5
          Re: Alienware 17 R5. Does not recognise LCD...

          What is the voltage on pin 28 with screen attached and disconnected and machine powered on?
          What is resistance to gnd on pin 28 when screen attached and disconnected?

          As you have changed the whole screen assembly then i see two possibilites at first:
          1. There is no pullup for the line
          2. The pch has failed on that pin and is pulling the line low.

          Most likely screen should pull the pin to ground when screen is connected. The mainboard checks for lcd on boot and does not post if lcd not connected.

          Or some other unknown error which we can not think of...

          Comment

          • Weelcup
            TopTech
            • Oct 2017
            • 300
            • UK

            #6
            Re: Alienware 17 R5. Does not recognise LCD...

            Originally posted by khaahk
            What is the voltage on pin 28 with screen attached and disconnected and machine powered on?
            What is resistance to gnd on pin 28 when screen attached and disconnected?

            As you have changed the whole screen assembly then i see two possibilites at first:
            1. There is no pullup for the line
            2. The pch has failed on that pin and is pulling the line low.

            Most likely screen should pull the pin to ground when screen is connected. The mainboard checks for lcd on boot and does not post if lcd not connected.

            Or some other unknown error which we can not think of...
            Hi
            Thanks for following up..
            Well pin 28 have 3.3v. Even when lcd is connected/not connected just after powring up.

            However, the +LCDVDD signal is missing. Which i think should be there before the lcd signal beck via DET.

            By following up. UV17 "LCD power controller" is not getting the enable signal. I mean the ENVDD is missing. Now the ENVDD is not shorted and the output is not shorted. So was trying to trace the ENVDD signal. But in the given schematics the ENVDD is privided by UV22 chip. UNFORTUNATELY, the board version that i have does not have such chip on board. I mean it is not in the board design. But when checking the enable pin on UV17 it gives 100k resitant to ground. Which is supposed to be so. Therfore, i was suspecting the pch. But not sure.

            I bought a bios dump online and flashed the bios but same issue. No LCDVDD.

            Comment

            • SMDFlea
              Super Moderator
              • Jan 2018
              • 20551
              • UK

              #7
              Re: Alienware 17 R5. Does not recognise LCD...

              Look around the board for a similar chip to UV22,there must be a multiplexer chip somewhere.
              Attached Files
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              Comment

              • Weelcup
                TopTech
                • Oct 2017
                • 300
                • UK

                #8
                Re: Alienware 17 R5. Does not recognise LCD...

                Originally posted by SMDFlea
                Look around the board for a similar chip to UV22,there must be a multiplexer chip somewhere.
                Thanks for the reply.
                I was seeking for the chip but could not find such chip. Giving the fact that the LA-F552P (my board) has a different PCH chip which is SR40E (CoffeeLake). compared to LA-D753P which have KabyLake PCH SR30W ... so was wondering if it still needs multiplexer chip!

                However, there is a Signal IGPU_ENVDD in the schematics i uploaded which goes to QG506 ... i checked resistans between the ENVDD & IGPU_ENVDD and it is only 2ohms. And was thinking it to be combined in this version!

                All the chips you mentioned in the photo are available in the La-D753p too. But not providing the enable signal.

                Comment

                • piernov
                  Super Moderator
                  • Jan 2016
                  • 4435
                  • France

                  #9
                  Re: Alienware 17 R5. Does not recognise LCD...

                  You have to measure +LCDVDD or ENVDD voltage while turning on the board. On some machines the voltage will fall back down if the display isn't recognized.
                  Sometimes the LCD power switch goes bad in a way that it's not fully shorted to ground but still cannot send out the correct voltage.

                  Also what's the history of the machine?
                  Last edited by piernov; 04-16-2020, 05:42 AM.
                  OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                  Comment

                  • Weelcup
                    TopTech
                    • Oct 2017
                    • 300
                    • UK

                    #10
                    Re: Alienware 17 R5. Does not recognise LCD...

                    Originally posted by piernov
                    You have to measure +LCDVDD or ENVDD voltage while turning on the board. On some machines the voltage will fall back down if the display isn't recognized.
                    Sometimes the LCD power switch goes bad in a way that it's not fully shorted to ground but still cannot send out the correct voltage.

                    Also what's the history of the machine?
                    Thanks for the reply,
                    I did turn on the board with attached probe on measure the enable signal and the output signal of uv17.

                    There are not output whatsoever. After couple of seconds the enable signal recieve only 0.2V and the output becomes 0.3v ... and that is it.

                    I have replaces uv17 with new one. But same issue.

                    The board history as i knew, was 19v shorred to ground. The cause was a cap. And been replaced. Then i found another short in pu500 the cpu controller. Also replaced. And that is it. Now it gives the lcd failure error.

                    One more thing to mention. It seems that the graphic chip have a seperate bios controller. UG13.. i was wondering if it is any related to the enable signal.
                    Attached Files

                    Comment

                    • Weelcup
                      TopTech
                      • Oct 2017
                      • 300
                      • UK

                      #11
                      Re: Alienware 17 R5. Does not recognise LCD...

                      Sorry in the above reply, i meant 0.2mV and 0.3mV respectively.

                      Comment

                      • khaahk
                        Badcaps Veteran
                        • Dec 2013
                        • 749
                        • Estonia

                        #12
                        Re: Alienware 17 R5. Does not recognise LCD...

                        I would make one more measurement to rule out that the lcd connector has bad connection:

                        1. Try to measure if the lcd assembly has pin 28 connected to ground (measure only on display assembly, not connected to mainboard.)

                        If yes then maybe the edp connector on the mainboard has pin 28 broken?

                        If not then i would just for the purpose of testing solder a jumper wire from pin 28 to gnd to see if pulling lcd detect signal low would make a difference.
                        I am assuming that the schematics is correct on the edp connector, otherwise might be bad idea.

                        Comment

                        • Weelcup
                          TopTech
                          • Oct 2017
                          • 300
                          • UK

                          #13
                          Re: Alienware 17 R5. Does not recognise LCD...

                          Originally posted by khaahk
                          I would make one more measurement to rule out that the lcd connector has bad connection:

                          1. Try to measure if the lcd assembly has pin 28 connected to ground (measure only on display assembly, not connected to mainboard.)

                          If yes then maybe the edp connector on the mainboard has pin 28 broken?

                          If not then i would just for the purpose of testing solder a jumper wire from pin 28 to gnd to see if pulling lcd detect signal low would make a difference.
                          I am assuming that the schematics is correct on the edp connector, otherwise might be bad idea.
                          Thanks for the reply.
                          I believe so. I mean pin 28 is the same as in the schematics.

                          I was not about this. And was wounder if it is safe to ground pin 28. Is that how the pch detect the lcd?

                          Just a bit worried to do so.

                          Thanks

                          Comment

                          • khaahk
                            Badcaps Veteran
                            • Dec 2013
                            • 749
                            • Estonia

                            #14
                            Re: Alienware 17 R5. Does not recognise LCD...

                            If the pinout of edp is correct then there should be no problem.
                            Did you measure the pin 28 resistance to gnd on the lcd assembly?

                            Comment

                            • Weelcup
                              TopTech
                              • Oct 2017
                              • 300
                              • UK

                              #15
                              Re: Alienware 17 R5. Does not recognise LCD...

                              Originally posted by khaahk
                              If the pinout of edp is correct then there should be no problem.
                              Did you measure the pin 28 resistance to gnd on the lcd assembly?
                              Thanks

                              Well, on the lcd assembly (disconnected from the motherboard) there is no measure . I mean the multimetre shows OL. Just like a seperated line.


                              The resistance to the ground, however, for pin 28 on the motherboard is 12.6k...

                              Comment

                              • khaahk
                                Badcaps Veteran
                                • Dec 2013
                                • 749
                                • Estonia

                                #16
                                Re: Alienware 17 R5. Does not recognise LCD...

                                So we have to assume that lcd det signal is not used on that model and forget about pin 28.

                                Comment

                                • Weelcup
                                  TopTech
                                  • Oct 2017
                                  • 300
                                  • UK

                                  #17
                                  Re: Alienware 17 R5. Does not recognise LCD...

                                  Originally posted by khaahk
                                  So we have to assume that lcd det signal is not used on that model and forget about pin 28.
                                  I see..
                                  I have checked the LCD_TEST signal. It flacuate between 0 and 1v while the lcd is disconnected and the board is connected to power source but not powered on. Then when i power it on (with the lcd disconnected) the LCD_TEST signal vanishs.

                                  One more thing i noticed is that the pin 36 INV_PWM signal is not provided but the pin is not shorted.

                                  So now ... the +LCDVDD and INV_PWM are both missing. Both provided fron UV22 in the schematics but my board does not have such chip.

                                  Comment

                                  • piernov
                                    Super Moderator
                                    • Jan 2016
                                    • 4435
                                    • France

                                    #18
                                    Re: Alienware 17 R5. Does not recognise LCD...

                                    DET is probably eDP HPD signal which the panel should pull high after turning on. (obviously require the panel to get 3.3V at least for a short amount of time)

                                    EDIT: sorry my bad, looked at the schematics and there is another line for EDP_HPD. So what I'm saying applies to EDP_HPD not DET.
                                    Last edited by piernov; 04-17-2020, 04:55 PM.
                                    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                                    Comment

                                    • Weelcup
                                      TopTech
                                      • Oct 2017
                                      • 300
                                      • UK

                                      #19
                                      Re: Alienware 17 R5. Does not recognise LCD...

                                      Originally posted by piernov
                                      DET is probably eDP HPD signal which the panel should pull high after turning on. (obviously require the panel to get 3.3V at least for a short amount of time)

                                      EDIT: sorry my bad, looked at the schematics and there is another line for EDP_HPD. So what I'm saying applies to EDP_HPD not DET.
                                      Aha!
                                      i will trace that signal and see...

                                      by the way, DET signal is 3.3v on la-d753p board but not in mine...

                                      thanks

                                      Comment

                                      • khaahk
                                        Badcaps Veteran
                                        • Dec 2013
                                        • 749
                                        • Estonia

                                        #20
                                        Re: Alienware 17 R5. Does not recognise LCD...

                                        There are ton of topics regarding alienware machines with nvidia gpu-s and w10 making lcd-s not working. The topics indicate that the edid information stored in panels get corrupted and then follows the LCD not detected error.
                                        But if you have tried working screen then that should not be the case.

                                        Check EDP data lines in diode mode to see if they measure the same.

                                        Comment

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