Unable to fix backlight -macbook pro 2017

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • imcool
    Member
    • Apr 2016
    • 18
    • Canada
    #1

    Unable to fix backlight -macbook pro 2017

    This A1708 macbook pro 13 2017 , 820-00840-A has no backlight but image is there,.

    I cant find the problem with backlight not working,
    Watched youtube videos as well for troubleshooting,

    Replaced following parts in backlight circuit
    - u8400
    - q8400
    - D8401
    - C8400



    still no backlight, only shows image
    I have 13V but no voltage on L8410, please check picture below to see measured voltage and resistance



    thanks
    Attached Files
    Last edited by imcool; 04-20-2021, 09:29 AM. Reason: added boardview and pdf
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 13938
      • Canada
      #2
      Re: Unable to fix backlight -macbook pro 2017

      Check the voltage on the Backlight ENABLE pin @ R8442. What is the reading?

      If that is on, most likely U8400 is defective and needs to be replaced. Wait, you have done this already.

      1) Remove the LCD display. Does this allow for the voltage to step up?

      2) What is the resistance to ground on L8410 ? Do this with the power off / battery removed.

      3) The voltage at the junction of R8401 and R8402 is not correct. This is a voltage divider that when R8402 is GROUNDED, the junction in the middle will LOWER the voltage from the source of 13v. That is, once this voltage divider is ENABLED, only then will Q8400 ENABLE. With the gate @ 13v = source voltage, Q8400 is remaining OFF.

      You can use one of the many online resistor voltage divider calculators to calculate the expected true voltage at the GATE (middle junction of this resistor voltage divider).

      4) How confident are you that U8400 is soldered correctly ?
      Last edited by mon2; 04-20-2021, 03:23 PM.

        Comment

        • imcool
          Member
          • Apr 2016
          • 18
          • Canada
          #3
          Re: Unable to fix backlight -macbook pro 2017

          i am pretty confident with my soldering as i repair cellphones(not screen) tristar audio ic and dead issues.
          I will check all that you suggested and return the results

          thhanks

            Comment

            Previous template Next

            Related Topics

            Collapse
            • Stephen
              A1466 MacBook Air 13" 2017 Backlight issue works but then turns off
              by Stephen
              Hello, got a weird MacBook Air here
              board looks fresh and no water damage, backlight works and turns on and stays on when installing OS etc. However, when the os is installed and when the system files are loaded before the login page the backlight goes out. I have wiped it, NVRAM reset, etc and even took some other instances and this blows my mind, never seen this before. Backlight just turns off once the OS is loaded. Anyone come across this and if so what would be the cause? I am certain its a board issue since I tested the LCD on another board and it stays on. Again the backlight works...
              08-23-2023, 09:12 AM
            • sofles
              Macbook a1707 2017 model 820-00928 GPU issue
              by sofles
              Hello there

              I have problem with Macbook Pro 15" 2017, model 2017, MB code 820-00928.

              I bought it as broken with some artefacts on the screen, first I thought that this is problem with ribbon cable but after inspectiing ribbon cable I know it is fine. I tried to reinstall macOs and then I figured out that this must be something with GPU as installation freezes at the end (when drivers are loaded). I installed Windows and was able to install every each of drivers except GPU driver, as soon as I tried to install GPU driver - black screen and restart.

              ...
              11-21-2024, 05:25 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
            • tommy97
              Apple MacBook A2337 - No backlight
              by tommy97
              Hi guys, I've got MacBook Air a2337 with no backlight. Once while testing it displayed with the backlight, however after restart problem come back.

              The laptop was tested with fully working screen.

              PP5v_BKLT_A/B 5V
              PP5v_BKLT_D 5V
              PP5V_S2 5V
              PP5V_SW_LCD 0.4V
              P5VS2_PWR_EN 1.8V
              P5VS2_BST_R 8V
              P5VS2_SW 5V
              PPBUS_5VS2_VIN 5V
              PPVOUT_LCDBKLT - Doesn't short 0V
              FP800 - Both sides 12v
              BKLT_EN_R & BL_PWR_EN - around 1.8v

              LP800 0.014V On both sides (should be 12? / no short)
              UC300 & UP800 Replaced...
              12-02-2024, 08:26 AM
            • Loading...
            • No more items.
            Working...