Start with the easier parts before moving on to the more difficult ones, which is the basic rule for fixing a phone. For one thing, difficult parts are more complicated and more risky to repair. For another thing, it costs more for difficult parts.
We here have a Samsung A50 won’t turn on. What is more, it cannot start up or charge when connected to a computer.
Generally speaking, there are five parts that might lead to the malfunction. Including: the battery and VBATT circuit, the power button circuit, the power supply ICs, the main power IC PWM, the main clock crystal oscillator.
Comparatively speaking, the main clock crystal oscillator is the smaller part. However, in the first place, we need to test these parts and find out which part has been faulty.
Tear Down The Phone
To test the faulty parts, we need to tear down the phone first.
- Insert a pry piece to take down the rear cover, and unbolt the screws with a screwdriver.
- Then use a pry bar to make a gap and take down the middle frame.
- Use a pry bar to disconnect the battery BTB, main FPC, display FPC and RF, and take down the motherboard.
- Lastly, take down the cameras.
Measure And Testing
Which part has been faulty? We apply exclusive method to find out the faulty part.
- At first, test the battery and VBATT. Measure the battery voltage with a multimeter, and the value is 4V. Hence the battery and VBATT circuit are normal.
- Next test the power button circuit, and the value is 1.371, which is normal either.
- Then heat up the shield cover on PWM IC at 370℃, wind power 60 and take it down. Test the current of the ICs for power supply. As a result, all values are normal. There is no short circuit happens.
- Apply a copper wire on VBATT and then connect it to DC power. When power on, the current is 0. Therefore we conclude that the issue is no current at startup.
Now there are only two parts left for testing and both can lead to no current issue. Which part should to be fixed to begin with?
Main Clock Crystal Oscillator Replacement
As the easily parts first rule, we should fix the main clock crystal oscillator in the first place. If not working , then fix the main power IC.
- Heat up the main clock crystal oscillator at 370℃, wind power 60 for a while
- Take it down with a tweezers
- Install a new main clock crystal oscillator
- Heat up the new crystal for a while.
Connecting to DC power, we measure the current again. As expected, the current becomes normal. Namely, the no current at startup issue has been fixed.
We install the phone parts back on the phone and test again. Beyond all doubt, the phone boots up successfully. So far, the Samsung A50 cannot turn on issue has been fixed.
Conclusion:
The key point here is to replace the main clock crystal oscillator first, instead of the main power IC. Whenever fixing a phone, always remember to fix the part which are easiest to repair.
Please check the following video for detailed process:
