We have received a Samsung A51 that won’t charge. Our client had it repaired at a local maintenance shop, but it didn’t get any better.Let’s get down to this work. First, we unbolt the screws after taking down the back cover, then disconnect all kinds of flex cables slowly and softly.
Dismantle the motherboard with tweezers. Take down the front and the rear cameras with this blue bar. We recommend this kind of stick with a flat head for convinient disconnection. Obeserve the motherboard and try to find out which part it had been repaired.
The traces shall be obvious. In today’s case we can see some deformations on the motherboard when we review the shooting part. Also, the CPU and power shielding cover shows has show some tear-down traces.In order to locate the exact error, we empower the logic board by currents and circuits.
Power on, no response. Then we measure the power voltage with a multimeter, the reading is 4.2V. That is to say, no power current. What are we going to do is to follow
this idea and take whatever measures that are needed to be done.
Disconnect the power, use a multimeter to see if there is any grounding shortcut happen to the capacitor and the inductor around the power. In this case, no abnormality. Don’t forget to do the same operation to CPU and UFS, no abnormality.
Therefore the power chip is not working. Set the hot air gun to 330℃，30 wind.Take down the power chip. Clean the bonding pad with a soldering iron and plate washer. Flatten the tin
on the power chip’s surface and clean it with plate washer.
After that, BGA the power chip.
Then trim it to the corresponding location on the motherboard, weld it with the hot air gun.
Install the phone and test it when the phone cools down. Power on, it’s functions perform well. Good for us.
For more detail, please check out this tutorial: