Jan "Jenkings" Škoda - blog

I received a phone call from a family member. At first, I had no idea what it was and I couldn't turn it on. Even after plugging in the charger, there was no power through the cable. As I thought it was working, I decided to check the battery first.

Unfortunately, after taking a quick look, I realised that it would be rather complicated. The phone itself is not as easy to access as phones used to be. I had no idea how to open it and was afraid that it was glued and that I would have to "cook" it. Fortunately, I tried using my nail and discovered a tiny gap. I used special tools to unclip the back of the phone. Even though I was really afraid of damaging the display because it bent a lot, I was eventually able to open it.



I also had to unscrew some covers inside and remove the tapes holding the battery in order to take it out. Then I saw the battery connector. It's a really fragile, small flex with an even weirder snap. At first, I measured it and found that it had a "nice" zero volts. I wanted to recover the battery, but as I had measured zero voltage, I had no idea about the polarity. Fortunately, I took a closer look at the connector and found that all its pins were labelled, which helped me to determine the polarity.



The next problem was how to charge it. I tried connecting the multimeter to my laboratory power supply, holding it for about ten or fifteen minutes while slowly raising the current to 'kick' the battery. Once the voltage had risen enough, I connected the battery back to the phone and quickly started charging it before the voltage dropped again. Fortunately, it worked and the phone started charging regularly.



I thought I had won when it was fully charged. I did a factory reset and everything worked. Except the fingerprint sensor. It was not detected or offered, and there was no mention of it in the settings either. As I thought, this was because I had unplugged the flex cable on the back cover where the sensor is located. I reconnected it and rebooted the phone. However, there was still no mention of the fingerprint sensor anywhere on the phone.

I tried doing one more factory reset to try to fix it. Fortunately, it was recognised and works perfectly. My guess is that the operating system is common to more models and, when 'installing' after a factory reset, it detects and lists the components. So, when you connect them later, they are not recognised.