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Malfunction of the backlight circuit can result in no backlight, half backlight, or won't turn on issues. For backlight issues commonly seen with iPhones, what's your solution? Hope our video today, the iPhone 7 Plus half backlight repair issue due to pseudo soldering of the display connector, will enlighten you on the subject.

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  1. Check the logic board carefully. Nothing goes wrong.
    • Check the logic board carefully. Nothing goes wrong.

    • Assemble the phone and test. The screen lights up and Apple logo appears. We can see with naked eyes that the right side of the screen is darker than the left side.

    • Judging by this, the fault might be related to the backlight circuit.

  2. Take out the logic board. Run diode mode measurement of backlight relevant pins on the display connector J4502.
    • Take out the logic board. Run diode mode measurement of backlight relevant pins on the display connector J4502.

    • The measured value of Pin 45 is OL, which is abnormal.

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  4. Open Refox. We can see that the voltage outputted from the backlight IC U4601 reaches Pin 45 of J4502 by way of C4602, FL4601 and C4605.
    • Open Refox. We can see that the voltage outputted from the backlight IC U4601 reaches Pin 45 of J4502 by way of C4602, FL4601 and C4605.

    • Continue to run diode mode measurement of C4602. The measured value is normal.

    • Judging by this, the abnormal value of Pin 45 is probably caused by open-circuited condition of its relevant circuit or malfunction of the display connector J4502.

    • Check J4502 carefully and we find that Pin 45 has been pseudo soldered.

  5. To further confirm the faulty position, detach J4502 from the logic board. Run diode mode measurement of the corresponding pad of Pin 45. The measured value is normal.
    • To further confirm the faulty position, detach J4502 from the logic board.

    • Run diode mode measurement of the corresponding pad of Pin 45. The measured value is normal.

    • We can confirm now that the fault is related to J4502.

  6. We can fix the problem by replacing with a new display connector.
    • We can fix the problem by replacing with a new display connector.

    • Clean the bonding pad and then solder a new display connector onto the board.

    • Please secure the four sides with Solder Paste for successful soldering.

  7. Now we can assemble the phone and test.
    • Now we can assemble the phone and test.

    • The phone turns on normally. The screen is also back to normal.

Phryne

Membro da: 17/11/2019

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