First let’s check out this phone.Connect it to USB, 40mA.Power on, it won’t turn on.
Heat the back cover for a few minutes and pry it out, unbolt the screws on the logic board.Apply the camera with this sticker,and then take down the fixing layer.
Disconnect the flashing lights cable,also the battery cable, the display cable, the charging cable and the fingerprint cable.Take down the camera module.
Observe the display cable and the motherboard, there is water-damaged trace.Measure the battery’s voltage with a multimeter, 2.7V, not enough.
Connect the display cable, the charging cable and the fingerprint cable.Connect it to the power and measure it’s power current.10mA, really weak.
Power on, the current changed, but the display didn’t show.Remove all the connectors.Take the motherboard down,the display connector and this bog shielding cover has been water-damaged.Turn it around,there are also some traces on this small part.Remove this big shielding cover and check out if there is any corroded parts.
Hot air gun settings:330℃, wind 30.Heat it and remove it.
Clean, no trace of water-intruded.Heat the small shielding cover and remove it.Take it down, the corrosion is rather severe.Clean it out with PCB cleaner.
Check out the diagram,we know that this resistor belongs to the main power-supply module.So it’s responsible for the power leakage.
Put the motherboard into the PCB holder,remove it after heating.Take the motherboard down and wait for its cooling.Connect it to the DC power and see if it still leaks.
No leakage.Power the battery.Apply some adhesive on the battery connector.Connect the positive pole with this red clamp,the negative pole with this black clamp.Charge it for a few minutes,measure it with multimeter, 3.65V.
Install the motherboard,connect all kinds of flex cables.Test the functions,all is well.
More details are as below: