Today we will share how to fix a Blackshark 3 that won't turn on. Press the power button and the phone is unable to turn on. Plug in the power cable and the phone is still dead.
Next, we need to take apart the phone for further testing. Place the phone back down on the heating pad at 100 °C for 2 minutes. Insert a plastic card and slide it through. Apply some alcohol to facilitate separation. Please don’t break the flex cable while lifting the back cover.
Disconnect the flex cable. Remove the shielding cover, speaker, and camera. Disconnect the antennas.
As the motherboard is fixed by a screw under the screen, we need to remove the screen before taking out the motherboard. Place the screen down on the heating pad at 100 °C for 5 minutes. Start separating the screen.
As the screen is separated, disconnect the flex cables. Remove the screen and motherboard. Then we connect the motherboard with a direct current supply. Trigger the boot-up with tweezers. The boot current jumps between around 100 mA and 200 mA. It can be judged that the pseudo-soldering of the CPU has caused the problem.
Next, we need to reball the CPU. Remove the shielding cover. Scrape off the thermal paste.
In order to remove the CPU, we need to cut a gap first.
Attach the motherboard to the holder and protect the flash memory. Remove adhesive with a hot air gun at 300 °C and airflow 80.
Then heat the RAM with a hot air gun at 380 °C and airflow at 120. While heating, try to pry up the RAM with a pry blade. You can remove the RAM once it becomes loose.
Keep heating to remove the CPU.
Then we apply some middle-temperature solder paste to the bonding pads. Neutralize the temperature of the bonding pads with soldering iron at 380 °C. Clean tin on the bonding pads with solder wick. Remove adhesive with a hot air gun at 300 °C. Clean the bonding pads with PCB cleaner.
Use the same method to clean tin and adhesive on the CPU. During cleaning, some capacitors will be erased. Please note that these are filter capacitors and do not influence the use of the phone.
Clean tin and adhesive on the RAM with solder wick. Remove residual adhesive with a hot air gun at 300 °C.
Reball the CPU. Apply some middle-temperature solder paste. Heat with a hot air gun to form the solder balls. Then recall the RAM.
The next step is to solder the CPU. Apply some paste flux. Align the CPU. Solder the CPU with a hot air gun at 350 °C and airflow at 100. Touch the CPU gently with tweezers. If the CPU returns to position, the CPU is soldered well. Then we solder the RAM. After the motherboard cools, apply some thermal paste. Put back the shielding cover and install the motherboard.
The phone vibrates and there is light on the edge of the screen. We can judge that the phone is able to turn on but the screen is damaged.
Then we install a known-good screen. The phone turns on normally. That’s as far as today’s repair goes. We will keep working on more Android repairs. Please stay tuned.
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