How Samsung Phone Service Center tried to cheat me

The Incident took place a year ago. My Father bought Samsung Galaxy On 7 around 2 years back and it was working fine for a year. And then a year later, he started facing frequent turn off problem. Initially when he told me about that, i just neglected thinking that the power button could have been accidentally pressed for a long time while having it in pocket resulting in turning off.

Once there was an emergency and I tried calling him. But the phone was actually switched off. For a long time, the phone was off. Then I went to his office directly and yelled at him for leaving the phone without charging. He told me that an hour back, the phone had around 72% of charge and he didn’t know that phone turned off after that. Then in turned off state itself, i put his phone in charge and it displayed charging symbol with 70%. Now, I got curious in finding out the reason for the turn off problem.

Block Diagram

Inside the phone, the Fuel Gauge ICs are used to monitor the battery voltage. Using a built-in Coulomb counter, these fuel gauge ICs calculate battery charge. SoC reads the battery voltage from fuel gauge via I2C Interface and then displays the battery voltage in the phone display.

Following were my deductions:

1. Since I was able to see the battery voltage in the phone display, there is no problem in the interface between Fuel Gauge and the SoC.
2. SoC reads the battery voltage and the software turns off the phone if the battery percentage goes to 0%. But in this case the phone was turning off even when the battery percentage was greater than 70%. If it had been a software bug, it would have resulted the same in all Samsung phones. But there was no such news. So, ruling out the software bug.
3. Is the Fuel Gauge good? Yes, while charging the phone when the turn off issue happened, it reported 70%. If it had been bad, it would have showed 1%.
4. So, Now my suspicion was on either loose contact in the battery connector or the battery must have gone bad.

Having those two suspicions, I visited the Samsung Service Center. The Technical guy called me that evening and told me that the motherboard had gone bad and it requires approximately around Rs.5000 to change the motherboard. I asked him the reason for his conclusions. He didn’t give any proper justification for his solution.

I explained to him on my deductions and asked him to check the battery connector and the battery. After a while, he rang up to me and said that both were good and only motherboard was the problem. I got on my nerves and asked him to just replace the battery alone which costs around Rs.1000.

And yes, my deductions were correct and then there was no such turn off problem.

Lesson:

1. Before giving the phone to get repaired at a service center, just get to know from your friends or from google on the possibilities of damage that could have occurred.
2. When the service center tells that some parts has to be changed, try to understand the technical information from them on why it needs to be changed.
3. Make sure that you are satisfied with the explanation given by the service center, else get to know the alternate solutions to repair.