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iPhone 6S no image/backlight

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  • iPhone 6S no image/backlight

    I had an iPhone 6S with no display at all. I had OL on the PP_LCM_BL_ANODE line. I replaced the usual filter and tried to rebuild the pad because they were loose and now i've continutiy all across the line and diode measurement is ok.

    When I boot, It goes from 0 to 0.65 amps and fluctuate. It's recognized by iTunes and display an popup telling me the iphone of ... is locked by a passcode.
    The screen is black but I can see some vertical line if I watch closely.

    I've tested all other pin from the connector and all looks like ok. Where should I check now since all lines seems fine.

    Thank you for your help

  • #2
    What's the history on this device? Have you check under the shield near BL ic, what value do you get in diode mode on backlight line? Did the coil take a shit? also check PP5V7_LCM_AVDDH


    • #3
      well, i bought the phone from someone but i don't know the exact history just he says the screen was not turning on but he can still ear the notifications, calls,... The inside is in perfect condition. I think he tried to replace a broken screen with cheap one without deconnecting the battery and blow the filter. YEs i've removed the shield on top of the cpu to test all the BL line

      for diode value i have :

      PP5V7_LCM_AVDDH 0.527
      PP_LCM_BL_CAT1_CONN 0.599
      PP_LCM_BL_ANODE_CONN 0.503
      PP_LCM_BL_CAT2_CONN 0.600
      Last edited by yauuik; 04-09-2018, 06:08 PM.


      • #4
        It's more than likely blown up the driver of it's had enough current to kill ferrites.


        • yauuik
          yauuik commented
          Editing a comment
          even with the correct diode values ? I've seen also sometime pin's from the connector are bent.

      • #5
        Just because it has the correct diode measurements it doesn't mean it's not damaged. A chip is a tiny little circuit inside. When you diode measure it you are only measuring the output or input circuits inside the chip. If some other area e.g the enable part of the circuit is damaged inside the chip it may not show up when you measure it.


        • yauuik
          yauuik commented
          Editing a comment
          I want to be 100% sure before removing the IC that's indeed the faulty part.

      • #6
        If you didnt have a short on the backlight anode line between the chip and filter then there is no mechanism for the backlight driver chip to be damaged. There was once a short at the connector but the filter popped which protected the circuit.

        To troubleshoot this phone, worry about image first and then backlight. Do you have image (with a backlight removed split screen and light shining from behind screen?)


      • #7
        Okay—so forget backlight and troubleshoot image. Stare at the schematic. What lines look like they control image power and image data? Let’s start with image power—list the lines that you think may be a part of image power


        • #8
          @Jessa_the_Professa For the image power, I would say :



          • #9
            Let’s delete the Panic B and chestnut pwr enable as data lines—something where a one or a zero changes a state.

            The others likely are power lines. From here you can either do a voltage test to confirm that power is present for image, or do a diode mode test in the connector to see if each line is short or open.