Honor 20 Pro does not boot issue repair process sharing.
Model: Honor 20 Pro
Announced: 2019, May
Defect Phenomenon
The phone just suddenly stops using during normal use.
No water damage, drop damage, or improper charging.
Troubleshooting
First, let’s heat the cell phone on the heating platform to separate the back cover.
Form a good repair habit, to protect the cameras with stickers.
Then remove the screws with the screwdriver carefully.
Then take out the motherboard to have a look
Oh my god! After separation, we found the phone has been repaired before
- some shielding covers are gone
- many chips are poorly soldered
- some small capacitors are even missing
The NFC chip is poorly soldered and not in the right position, small components around it are also missing…
There are so many problems on the motherboard, some areas are so messy.
Anyway, let’s fix the problems one by one.
Repair Process
First, remove the NFC chip. After removing the NFC chip, deal with the pads on the PCB.
Connect the motherboard with the DC power supply and try to boot it
Trigger the boot process with tweezers, there is a small current leakage, and the pointer swings back and forth.
This current value indicates there is a current leakage on the second power supply rails.
Let’s apply it with the DC power supply again, and inspect under the thermal camera carefully.
After checking, we find the abnormal hot area.
In order to find out the exactly damaged component, let’s use the rosin inspection method to check
- Apply rosin to the hot area
- Connect the motherboard with the DC power supply with a proper voltage
Find out the shorted component easily
This is a filter-type capacitor, let’s just remove it directly first.
And when removing this capacitor, we find the small inductor around it is also damaged.
Let’s replace the inductor with a new one
(this inductor as we mentioned before, though it looks a little bit different from the original one, the specification is the same)
Then connect with the DC power supply and test again, this time the phone can be booted normally.
Then let’s assemble the phone to have a test.
The phone cannot be booted if the battery cannot be detected, so before connecting the battery, let’s measure the battery voltage
The voltage on the battery is OK
The phone can be booted normally, charging function is also works fine.
The only problem is the NFC not working. (as we did not solder back the NFC chip yet)
Since the data is more important for the client, so before fixing the NFC chip, for safety considerations. Let’s back up the data first.
For the NFC function repairing, we just need to take the same model donation board and swap the chip and components one by one.
All the small components around the NFC chip as well as the NFC chip have been soldered properly.
Last but not the least, let’s solder back the shielding covers
Assemble the phone and test, the phone can be booted normally.
The NFC function is also back to normal.
