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iPhone 6 no image - 2 volts on C1502 after chestnut replacement.

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  • iPhone 6 no image - 2 volts on C1502 after chestnut replacement.

    iPhone 6 no image. Customer didn't have much previous history on the phone because it was his girlfriend's phone. He just said the phone wouldn't turn on, they took it to another shop where they try with a new screen but with no luck.
    The phone HAS backlight and gets detected by itunes, ask for "trust" the device, everything seems normal there.

    Actions taken: tested new screen. Measured J2019 connector with diode mode, everything is OK comparing with a KGB. Measured voltage on C1502 to check voltage from PP6V0_LCM_BOOST line, and it was 1.6 volt so I replace chestnut. The installation was smooth and straightforward but I still have no image after installing the new chip.

    The phone is in the very same state: recognized by itunes, asks to trust PC, and now C1502 measurement is 2,0 volts. I tried to find something else in the schematics but Im a little lost now.

    How should I proceed?

  • #2
    I have no idea what the normal voltage reading is on PP6v0_LCM_BOOST is supposed to be and when, so I wouldn't consider the 1.6v or 2v0 to be low unless a KGB had a higher steady voltage on that line. Just because the name of that line is PP6v0_LCM_BOOST is doesn't imply "This line should be 6v all the time" I would also check diode mode on that line and compare.

    The signature failure for no image on an iPhone 6 is Long Screw Damage---have you ruled that out?

    If I had a 6 with no LSD, no image, all normal diode mode readings, and same after chestnut change, I would look to see if I had any connector damage, even very minor, that would prevent the pins from making good contact. I would check on the arrival of all image related power voltages at the LCD connector with voltage readings near the connector---soldering wires if I had to in order to take these measurements with a screen attached then go from there.


    • #3
      SOLVED! I couldn't sleep last night thinking about the schematics for this phone. I had discarded everything including LSD.
      Suddenly it hit me: the only thing I hadn't check yet was C1554. Diode mode readings were different from the KGB, so I reaplaced the cap and now is on!!
      Thanks for the help because I used your recommendation: "remember all your previous repairs". I solved a case exactly like this with Mark and you when I was on PBRS!


      • Jessa_the_Professa
        Jessa_the_Professa commented
        Editing a comment
        Excellent---I remember that phone, it died on the hotel bed. I'm glad that it gave it's life to help you fix this phone.