We have received a Huawei Mate20 Pro. It’s 5G WIFI can be found. However, key in the password, connected success, no signal.
Power off. Pry out the back cover after heating it with a hot air gun. Take down the back cover. Along together unbolt the screws.
Camera stickers on.
Remove this fixing layer. Disconnect the flash light cable with this pry bar, also the battery cable, display cable, charging cable, power cable, ear phone cable and sensor cable.
Remove the front camera module, the motherboard and the rear cameras module.
Turn it around, take down the shielding cover and observe the WIFI chip, no water-damaged trace, but R5203 has been corroded badly.
Brush the dirt off, put the motherboard onto this PCB holder. Weld R5203 off with the same hot air gun(330℃, wind 30).
Its bonding pad has been corroded badly. We add some tin with a soldering iron and clean it off. Scrape off the dirt with tweezers.
Apply some tin and the paste flux. Melt the tin, then connect the two poles of this resistor with liquid tin. According to the corresponding diagram, R5203 should be 0V, so we can connect these two poles.
Get it cleaned, measure its reading with a multimeter.
260V, the work is done.
Install the rear cameras module and the motherboard. Connect these cables.
Power on, key in the password. Settings—WIFI, connect 5G WIFI.
Connected, signal works. Tiktok is working.
Peel off the camera stickers. Install the fixing layer, the screws.
Apply some glue on the frame. Elastics on. Problem solved.
Attached link as followed: