Jan "Jenkings" Škoda - blog

A few days ago, a colleague gave me some mobile phones, one of which was a POCO M3. It's not an old phone and it's in perfect condition. When he gave it to me, it was like brand new. Even the factory sticker on the back of the phone was completely untouched. I decided to use it as a test device for app development.



I was even more surprised when I found out what would happen if I turned the phone off. But let's start from the beginning. First, I made my way through all the setup and welcome screens, which took quite a long time. I also downloaded and installed accumulated system updates, so the phone rebooted a few times. Everything seemed to be working fine. I turned the phone off to come back to it the next day. However, when I took it the next day and tried to turn it on, nothing happened. Even the consumption on charger was exactly 0mAh, I tried all the combinations to force a reset, but it had no effect.

So I did some research online and found out that this phone is quite famous for its tendency to deadboot. In other words, there's nothing you can really do with it. The phone just has a tendency not to boot up again after a normal shutdown or restart. As the phone has no reset button to disconnect the battery, the only non-destructive option mentioned was to let the battery run out completely and then charge and turn the phone on again. However, even after a few days, nothing had changed, so I decided to try to fix it myself.

As the phone was brand new, I had to be very careful when disassembling it to ensure I did so precisely and carefully. Fortunately, the phone is not glued, just clicked together, but the back was fixed on really strongly. It took me about half an hour to carefully open it without damaging the display or the plastic.

In the end, I'd say I was 99% successful. There are no scratches after I put it back together, and the joint is only slightly bigger than before. It's not something you'd really notice when you look at it.



So, what have I done? I carefully took out all the flex cables from the motherboard, removed it and unclicked the shielding sheets. Some sheets also needed to be desoldered. With maximum concentration, I took them out, applied flux, and tried to heat every part that could cause this issue (I found out which parts were responsible for the issue online). This was really tricky as the board has components soldered on both sides. I had to heat the correct side just enough in the hope of fixing it without heating it too much and letting the components on the bottom side fall down, as I would definitely not be able to mount them back on as they are incredibly small.

Fortunately, everything went well. I soldered and clicked the sheets back in place, temporarily connected all the flex cables, and tried turning and restarting the phone many times. It seems to be working, so I connected and screwed everything back in place, put the cover back on, and rebooted the phone a few more times. Everything still works. So I hope it will work!