thread top ad

Collapse

Announcement

Collapse
No announcement yet.

820-3332 no video/backlight

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

  • 820-3332 no video/backlight

    Hi Team,

    This machines starts, chimes but no display on internal or external screen.
    Checked and noticed that F9700 was blown, so I replaced it, after what PPBUS_S0_LCDBKLT_FUSED was present but still no backlight display.
    LCD_BKLT_EN: 0V
    disconnected the screen at J9000 and tested again on external screen: OK
    Tried another 2013 retina LCD Screen: NOK

    reflowed U9100:
    LCD_BKLT_EN: 3.3V OK
    now with the LCD connected PPBUS_S0_LCDBKLT_FUSED jumping between 1.8V to 3.0V, if LCD not connected it stays solid 12.50V
    PP5VR3V3_SW_LCD at L9000: 5.0V
    If I put a torch light on the LCD, I DO have a Display/Image.
    Should I suspect u9701?

  • #2
    Check diode mode to ground on D9701 pins w/ and w/o LCD connected.

    Comment


    • #3
      Did you resolder U8900?

      Comment


      • #4
        JohnB8812 :

        Yes resoldered the pins with good flux and solder

        2informaticos:

        In diode mode without LCD Connected:
        D9701 to gnd:
        Pin1: 0.880V Pin2: 1.191V
        and the same reading with LCD Connected:

        Comment


        • #5
          Are these diode mode readings with red probe at ground?

          PPBUS_S0_LCDBKLT_FUSED is practically same as PPBUS_G3H.
          Did you note PPBUS_G3H fluctuating too???

          Comment


          • #6
            Yes red probe on ground.
            Ppbus_g3h solid 12,5V
            That why I think the fuse was blown, maybe U9701 randomly shorting lcdblkt_fused rail to gnd or having dropping the resistance of that rail close to gnd (low résistance to gnd)

            Comment


            • #7
              Change the fuse then...

              Comment


              • #8
                Hi 2Informaticos,
                you were right the fuse was blown again, so I replaced it.
                After what PPVOUT_SW_LCDBKLT was mesuring 55V which means that the backlight boost circuit is working.
                I've tried a spare lcd: worked fine
                So I disassembled the faulty LCD, then I've found that it had a WD + burn and broken and missing PPVOUT_SW_LCDBKLT pin on the LCD connector.
                See attached pictures.
                Maybe I can try to fix it
                .......
                Thank you

                IMG-20191108-WA0005.JPG20191108-002811-677.jpg

                Comment


                • #9
                  You can try, nothing to lose before trash it...

                  Comment

                  thread bottom ad

                  Collapse
                  Working...
                  X