Macbook Pro A1502 820-4924A no backlight

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • drscoot
    Member
    • Dec 2020
    • 44
    • Belgium

    #1

    Macbook Pro A1502 820-4924A no backlight

    I've been testing for several hours at this board, including most tips from Louis video https://www.youtube.com/watch?v=nH-mWAt0CDI
    But still no luck, screen is there but no backlight. Also no fan spin, but maybe that is temp regulated? HDMI is OK.
    There were some minor stainmarks around the lcd connector, but the white dot is not red.
    So far I found this bizar; with only the lcd connected, on the caps in the PPVOUT_S0_LCDBKLT circuit (that goes to pin1 of lcd connector), all these caps measure short to ground on both sides! When I disconnect the lcd cable only 1 side of the caps is to ground. I check at the 2 sets of 7 large caps, like C7760, C7770...
    I'm wondering if that is normal behaviour, or is there something wrong with the lcd-(cable)?
    When I measure at the lcd connector on the logic board pin1 is MOhm to ground. And pin1 on the cable is only 2.5Ohm.
  • mon2
    Badcaps Legend
    • Dec 2019
    • 14050
    • Canada

    #2
    Re: Macbook Pro A1502 820-4924A no backlight

    With the LCD cable removed, what is the voltage reading of PPVOUT_S0_LCDBKLT ?

    If U7700 and supporting components are working correctly, this switching boost regulator should be supplying a higher voltage than its input of PPBUS_G3H. Should be 25V++.

    I believe that you should see this higher voltage even without the LCD screen mated @ J8300.

    Inspect the LVDS cable for any possible shorts.

    Comment

    • mon2
      Badcaps Legend
      • Dec 2019
      • 14050
      • Canada

      #3
      Re: Macbook Pro A1502 820-4924A no backlight

      I think the display is required to enable the backlight.

      Is the LVDS cable removable on both sides of the cable?

      Comment

      • drscoot
        Member
        • Dec 2020
        • 44
        • Belgium

        #4
        Re: Macbook Pro A1502 820-4924A no backlight

        thanks for the reply,
        With the lcd cable disconnected from the LB, I measure no voltage at pin 1 of J8300. I suppose the lcd needs to be connected before there is a voltage on pin 1.
        btw. the bare LB draws at startup about 0,7A and after about 2min it is 0,25A
        Now I have a look at the other side of the lcd cable.
        Last edited by drscoot; 04-28-2021, 01:11 PM.

        Comment

        • drscoot
          Member
          • Dec 2020
          • 44
          • Belgium

          #5
          Re: Macbook Pro A1502 820-4924A no backlight

          Well I made some progress, on the lcd side the LVDS connector was corroded.
          I was able to clean both Male and Female sides, if I now measure resistance on pin1 of the cable at the LB side I have 15 Ohms instead of 2,5 Ohms. Both with lcd cable not connected to the LB. Once connected, still no BL and continues reset, I hear the bong sound every so seconds. W/O the lcd connected, normal boot.
          So it looks like the cable or the lcd board has something more wrong.
          I'm wondering what the normal expected ohms value is of pin1 at the LVCS cable?

          Comment

          • mon2
            Badcaps Legend
            • Dec 2019
            • 14050
            • Canada

            #6
            Re: Macbook Pro A1502 820-4924A no backlight

            Even @ 15 ohms, sounds low for the backlight led rail but never personally measured it.

            Is this a screen where you can open up to the board (T-conn?) on the display itself?

            Have seen some scary videos on the many layers of the display.

            For some inspiration:

            https://www.youtube.com/watch?v=1CzM0SRtX6U


            https://www.youtube.com/watch?v=O2j4tDv8jRU

            Comment

            • Stephen
              Meow Meow MEOW!
              • Apr 2020
              • 667
              • United States

              #7
              Re: Macbook Pro A1502 820-4924A no backlight

              The cable on these models is replaceable and is easy to replace. I would suggest replacing the cable. It is very common for the cable to fail in situations. Also have you checked the Backlight fuse? And also if you replace the Cable and the Backlight fuse is not blown, I am going to suggest replacing the LVDS connection because that is most likely the culprit.
              sigpic
              MEOWING IN THE IMPOSSIBLE UNIVERSE!

              Comment

              • drscoot
                Member
                • Dec 2020
                • 44
                • Belgium

                #8
                Re: Macbook Pro A1502 820-4924A no backlight

                Well the connector was corroded at the lcd side, after cleaning the resistance changed, but still not working. After some closer looks, it seems that the outer pin (pin1) is partly missing at the cable side near the lcd.
                So yes new cable on its way, hoping that the screen side connector is still OK

                Comment

                • Stephen
                  Meow Meow MEOW!
                  • Apr 2020
                  • 667
                  • United States

                  #9
                  Re: Macbook Pro A1502 820-4924A no backlight

                  if the screen side connector is bad it is repairable. You will have to use a Solder Flat Blade tip to remove the LVDS connector on the LCD. Do not use a heat gun or you will melt the connections and burn your LCD.
                  Last edited by Stephen; 04-29-2021, 07:16 PM.
                  sigpic
                  MEOWING IN THE IMPOSSIBLE UNIVERSE!

                  Comment

                  • drscoot
                    Member
                    • Dec 2020
                    • 44
                    • Belgium

                    #10
                    Re: Macbook Pro A1502 820-4924A no backlight

                    I adding some microscope shots of the connector. It looks like pin1 is completely gone on the cable. Also the screen connector looks bad, not sure if that's still good to go? I think there is some melted metal behind the outer pin, that blob?
                    When I look at the boardview, J8300 has 43 pins, here I see 30, how?
                    Pin2 on the board seems desoldered, but wait boardview says it is unconnected...
                    Attached Files
                    Last edited by drscoot; 04-30-2021, 04:27 PM.

                    Comment

                    • ACS-Repair
                      Badcaps Veteran
                      • Feb 2021
                      • 203
                      • Canada

                      #11
                      Re: Macbook Pro A1502 820-4924A no backlight

                      Definitely your LVDS cable is toast. unfortunately, I suspect that the connector on the display is bad as well. The "blob" you are seeing on that connector is melted plastic coming through the back. As Stephan says, you will need to replace that screen connector.

                      Comment

                      Related Topics

                      Collapse

                      • Comp_Pro
                        No Backlight Macbook A1990 820-01041
                        by Comp_Pro
                        Hello all,

                        Am trying to figure out this backlight issue with this A1990 Macbook Pro.

                        Tests performed:

                        There is no backlight even with a good screen.
                        Backlight IC is receiving the correct support voltages.
                        Fuse F8400 ok
                        Current sense resistor R8400 ok
                        Backlight IC is receiving 3.3V on enable pin.
                        Backlight IC receiving voltage from PPBUS_G3H, aprox 12.5V.
                        Backlight IC receiving 5V from PP5V_G3S
                        Backlight IC BKLT_SCL and BKLT_SDA both measure 0.545V diode mode to ground
                        I2C_BKLT_SCL and I2C_BKLT_SDA both measure...
                        05-06-2024, 10:23 PM
                      • sdogs
                        Macbook A1502 820-3476-a no backlight
                        by sdogs
                        Happy Sunday guys ;-)
                        I have a macbook pro 13 A1502 on my hands with a backlight problem.
                        After the measurements I noticed that PPVOUT_S0_LCDBKLT shorted to ground, in order I removed the following components:
                        C8300 and C8303 and always at pin 1 of both short circuit present;
                        D7710 short circuit present at pin 2;
                        R7731 and R7732 and short circuit always present;
                        C7713,C7714,C7715,C7716,C7717 and short circuit always present;
                        I also replaced the LVDS connector but the result hasn't changed, even without the connector on the logic pin 1 is shorted..... what...
                        07-16-2023, 09:47 AM
                      • Instafixx
                        Macbook Pro A1502 820-4924A BACKLIGHT ISSUE
                        by Instafixx
                        Hello,
                        i have a Macbook A1502 with No Backlight but the image is on as confirmed by a flashlight.

                        the macbook was dirty so i went ahead and cleaned it. the light back on for a couple of minutes and now its again back off.

                        The resistance of the Pins at j8300 look okay as confirmed by tallying from a donor board.

                        I think its a mosfet issue with the Q7701 but never quite understood how these things work.
                        Can anyone guide?
                        12-31-2022, 01:38 AM
                      • Constantinos
                        Macbook Pro A2442 820-02098 No image but has backlight
                        by Constantinos
                        Hi all
                        I have a Macbook Pro A2442 with the 820-02098 from a friend which has no picture on the display, however, the backlight works.
                        He was streaming a football match on a questionable site, then the site crashed, and the problem emerged.
                        Initially, he sent it to apple, who quoted him £1323.95 to replace the display, lid angle sensor and top case.
                        Obviously, he decided against this and gave it to me so that I could have a crack at it.
                        From initial diagnostics, I connected to an external monitor, I first tried with a HP 22W monitor, and I booted into the boot menu...
                        08-24-2024, 09:48 AM
                      • francescoranchi
                        MacBook Pro A1909 LCD (no backlight)
                        by francescoranchi
                        Hello Everyone,
                        I'm looking at purchasing a used LCD from ebay for my macbook A1990 2018 15inch which LCD I cracked. Since new / used but working displays cost around 500$ , I found a Grade A+ LCD display for A1990 which has a good price of 110$ but has no backlight.
                        I would need just to make sure that what I know/my reasoning is correct:

                        - No backlight means flexgate issue, therefore changingthe flexcable would be enough (I can microsolder to fix the flexgate problem, done it a few times already)
                        - Seller confirmed its a LCD issue, and not an issue with the...
                        12-04-2023, 06:46 AM
                      • Loading...
                      • No more items.
                      Working...