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Inleiding

The CPU of mobile phones functions just like the brain of our body. Which makes CPU repair the most complicated subject in mobile phone repair.

Video overzicht

  1. Press the power button to turn on the phone. There is no response at all.
    • Press the power button to turn on the phone. There is no response at all.

    • Measure the boot current first. The current pointer moves from 0 to 50mA-60mA and then stays still. Connect the phone with computer. The phone can not be recognized.

    • USB IC or power supply of the logic board might have malfunctioned. (Why? You can check out the boot circuit explanation here)

  2. First thing we do is to measure power supply of the logic board.
    • First thing we do is to measure power supply of the logic board.

    • Measure the 16 rails of logic board power supply. The measured value is normal.

  3. Nintendo Switch-kits

    Een snelle oplossing die je weer mee laat doen

    Koop Switchkits

    Nintendo Switch-kits

    Een snelle oplossing die je weer mee laat doen

    Koop Switchkits
  4. So our next move is to replace the USB IC with a new one and see how it works.
    • So our next move is to replace the USB IC with a new one and see how it works.

    • Detach the USB IC from the board with Hot Air Gun. Clean the bonding pad afterwards.

    • Solder a new USB IC and test again. The problem remains unresolved.

  5. We can confirm now that CPU has pseudo soldered or damaged. Let’s re-solder CPU and see how it works.
    • We can confirm now that CPU has pseudo soldered or damaged. Let’s re-solder CPU and see how it works.

    • Remove the shield plate with Hot Air Gun. Stick High-temperature Tape on components around CPU. Then detach CPU from the board with Hot Air Gun. Clean the bonding pad and remove solder on CPU afterwards.

    • Get CPU reballed. Once done, wait for the CPU to cool for 2 minutes. Apply some BGA Paste Flux to the bonding pad. Get the reballing finished CPU in position and solder with Hot Air Gun.

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

    • The phone turns on normally. Run function test. All going well. Problem fixed.

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Phryne

Lid sinds: 17-11-19

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