Announcement

Collapse
No announcement yet.

iMac 21,5 Late 2013 A1418 (EMC 2638) Display dead no 4th Diagnostic LED

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    iMac 21,5 Late 2013 A1418 (EMC 2638) Display dead no 4th Diagnostic LED

    Hello,
    I'm trying to repair an iMac A1418 (EMC 2638) which display fault.
    Seems on cold boot display works fine but after a while begins to flickering to a black screen.
    I tried an external monitor and it works, correctly.
    The board is a 820-3588-A (files attached).

    When the display is active and alive, I think all values are ok:
    Diagnostic LED: #1 ON #2 ON #3 ON #4 ON

    J8100
    LED_RETURN_1 4,5V (sometimes 11,5V)
    LED_RETURN_2 4,5V (sometimes 11,5V)
    LED_RETURN_3 4,5V (sometimes 11,5V)
    LED_RETURN_4 4,5V (sometimes 11,5V)
    LED_RETURN_5 4,5V (sometimes 11,5V)
    LED_RETURN_6 4,5V (sometimes 11,5V)
    BKLT_BOOST_1 61,3V
    BKLT_BOOST_2 61,4V

    L440
    PP12V_LCD_F 12,1V
    PP12V_LCD 12,1V

    When suddenly the display goes black, I have:
    Diagnostic LED: #1 ON #2 ON #3 ON #4 OFF

    J8100
    All 0V

    L440
    PP12V_LCD_F 12,1V
    PP12V_LCD 12,1V

    VSYNC Cable with no sign of shorts.

    Any hint?
    Thanks
    Attached Files

    #2
    Re: iMac 21,5 Late 2013 A1418 (EMC 2638) Display dead no 4th Diagnostic LED

    Nobody can give me some tips?

    Comment


      #3
      Re: iMac 21,5 Late 2013 A1418 (EMC 2638) Display dead no 4th Diagnostic LED

      If you using a flashlight do you see anything on the screen?
      Looks like faulty backlit.
      Following Apple repair manual if no #4 LED but works on external display then replace LCD panel.
      Laptops and computers repair.

      Comment


        #4
        Re: iMac 21,5 Late 2013 A1418 (EMC 2638) Display dead no 4th Diagnostic LED

        when the screen goes black, there is nothing visible under a flashlight

        Comment


          #5
          Re: iMac 21,5 Late 2013 A1418 (EMC 2638) Display dead no 4th Diagnostic LED

          i have this kind of problem also anyone have advise?

          Comment


            #6
            Re: iMac 21,5 Late 2013 A1418 (EMC 2638) Display dead no 4th Diagnostic LED

            @vougheart - what is the history of this box ?

            Was working one day and then no display the next ?

            Is the full display dark ? Any graphics; pixels or lines on the screen ?
            Last edited by piernov; 04-12-2022, 07:52 AM. Reason: gpu cooking bullshit as usual

            Comment


              #7
              Re: iMac 21,5 Late 2013 A1418 (EMC 2638) Display dead no 4th Diagnostic LED

              I bought a new display and works fine until now (3 years)

              Comment

              Working...
              X