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820-3115 No Backlight No Video

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  • 820-3115 No Backlight No Video

    Hi. So, I have a board here that came in with no backlight, but had full video. I replaced C9020 and C9796 because they looked burnt. Also L9080 was missing completely so I replaced that as well. Turned the laptop on to see if it made a difference and I got a chime with a quick flash from the backlight and no video whatsoever. Just darkness. Started measuring around and this is how far I got before things got worse.

    U900 PN 4,5 3.2V
    LCD_IG_EN 3.2V

    Upon measuring pins 2,3,4 on LVDS voltage started at 3.3 and dropped until I noticed that L9004 had pretty much imploded into a bubble at some point during taking measurements. Right now it looks like it could be welded to the board and C9015, C9010 and L9008 dont look so great either. Thanks for any help in advance. Have a good one.
    Last edited by RyanLEN; 05-11-2017, 10:21 PM.

  • #2
    Replace all burned and bad looking parts and check LVDS connector, could be shorted inside, my advice is replace it......

    After check all this connect your display, do not plug magsafe yet!!!

    Check for short in diode mode on L9004, L9008 and on C9020, if no short found, plug magsafe..........

    Report result.....

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    • #3
      Came downstairs this morning to this... This usually takes a long time and cursing for me. does anyone have a method for this that isn't painful?

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      • #4
        Replaced everything. No short. Now I have same backlight flash at startup but now with horizontal stripes which stay when the backlight turns off.

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        • #5
          Voltage on both sides of L9004?

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          • #6
            Hi. PN 1 - 3.19
            PN 2 - 3.15

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            • #7
              Known good LCD? Take a picture of the LCD so I can see?

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              • #8
                Here is the 1 second of flash before backlight goes off. When I first got this in the only issue was no BKLT. I had full video. I was able to access Recovery mode and diags. Could the demise of L9004 possibly killed my LCD. I am obviously hopingthat not the case, but thats kind of what its looking like. Thanks alot for your help. Have a good one.

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                • #9
                  i would try a known good lcd/cable next.

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                  • #10
                    It seems like coincidence that I am having this issue after board damage. Going to give it a shot. The only thing I have handy is a late 2012 Retina A1425 Not sure that will work. Never tried.
                    Last edited by RyanLEN; 05-13-2017, 11:49 AM.

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                    • #11
                      That is either a bad LCD/cable or 3.3V not getting to the LCD and the LCD getting like 2.5V or something around that value. No a retina LCD is totally different of course.

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                      • #12
                        Thank you guys. Appreciate it!

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                        • #13
                          Hey Guys. I have tried a known good working screen and cable with same result. Thank you.

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                          • #14
                            im sorry. not the same. I get a quick flash of back light then black. no video no back light. thanks.

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                            • #15
                              Voltage on C9015 and C9020?

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