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820-2936 no image

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  • 820-2936 no image


    I've got this board thats chime ok but there is no backlight or image.

    pin 1 u9000 is 0 v

    lvds pin 8-18 diode mode

    Pin8 0.620
    Pin9 0.620
    Pin10 0.000
    Pin 11 0.620
    Pin12 0.620
    Pin13 0.000
    Pin 14 0.620
    Pin15 0.620
    Pin 16 0.000
    Pin17 0.620
    Pin18 0.620

    external monitor works.

    any suggestions?

    is it u1800 that is bad or is it something with lid?

  • #2
    Have you tried another display assembly?? It is water damage?? if yes inspect LVDS connector if it is evident water damage replace connector first...


    • #3
      The important pins here are 4 6 and 7. 4 should have 3V and 6 and 7 should check the same on diode measurement. Also make sure SMC_LID is high.


      • #4
        No water. Display is working.
        I repaired this computer one year ago. Replaced ISL6259 and put a jumperwire between pin 17 and c7050. Then I sold it for 380$. Then I bought it back for 80$ as defect but I didnt know it was the same until i got it home and opend it. The seller said that it worked great for almost a year after she bought it from me.


        • #5
          SMC_LID is 3.4 v

          Pin 4 3.3v

          Pin 6 0.620
          Pin 7 0.620


          • #6
            Looks ok. Now try with a separate LCD cable and see if pins 4, 6 and 7 make it to the other side. I suspect a bad pin 4 in the connector so no 3V to the EEPROM in the LCD.
            Did you do a PRAM reset just to be sure?
            Do you have another LCD assembly to test? 2008-2011 models should all work.


            • #7
              I have multiple lcd assemblies but it makes no differense. Tried a separate cable, it was hard to meassure but everyting was ok.

              Don't you think it has anything to do with U9000 as I have 0v on pin 1, ON. LCD_IG_PWR_EN . I have 0 volt on U9000 output


              • #8
                Pin 2 and 3 on u9000 have pp3v3_s5


                • #9
                  LCD is not detected. LCD detection is through pins 6 and 7 data bus. Did you measure 6 and 7 with LCD unplugged? What is the resistance between pin 6 and 7?


                  • #10
                    Thanks alot for helping me.

                    it meassures the same both with and without the lcd connected. resistans between pin 6 and 7 is 4.37k


                    • #11
                      Just did a test here. Diode mode without LCD .615 and LCD plugged in it drops to .560. Better check your readings again. I suspect a bad LCD connector. The 4.4K between the pins is OK.
                      Last edited by dukefawks; 09-03-2016, 02:37 PM.


                      • #12
                        diode lvds unconnected

                        pin 4 0.349
                        pin 6 0.614
                        pin 7 0.613

                        connected is same.

                        didn't diode check pin 4 erlier. is it reading to low?


                        • #13
                          Pin 4 is fine as long as there is 3V and it will not drop with LCD connected. Pin 4 and 6 should drop if you plug in an LCD. Try other LCD assemblies to see if there is any difference. Try again with just a cable and see if pin4 and 6 come out the other end


                          • #14
                            Good Morning.

                            pin 4,6,7 is all 3.3 volt at the loose end with just a cable. Same measurements at connector both with and without lcd connected. when lid is closed i get 0.063v at 4,6,7


                            • #15
                              Lid open or closed should not matter on pin 4 as it is connected to 3V_S0. Check again to be sure. Did you do a PRAM reset?


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