1 Is it true that it is a motherboard issue?
I have had a Mi 9 since August, 2019. In feburary, suddenly my phone started to randomly shut down, and I could not restart it sometimes. Once I could not turn on, just for half day, and then totally died.
I visited a phone service, who said it’s a motherboard issue (maybe charging IC), and it’s dead. I went home, put it on charger and IT WORKED. Worked till 2020 July (almost half year after it was said it’s useless).
Now it showed the android logo, then turned off. Sometimes it booted correctly, then turned off. It was a bootloop, but if I let it to loop a lot of time after half an hour it started. After few hours of totally perfect use, it died again. Then I flashed and used MiFlash. It could not be turned on. I could only reach fastboot (still loop). When battery drained, I visited services, all of them said it’s a motherboard issue.
Is it possible to die like this? I think it’s more likely battery doesn’t fit well or something.
Ist dies eine gute Frage?
1 
2 Kommentare
I had exactly the same problem with the mi 9 of my mother in law, it randomly shuts down, i thought it was battery, i change it, same thing, until one day it died completely.
I completely solve it by, using a heat gun, take out the IC Charger RF shield and using some solder flux on the area, i heat the entire charger area, until i saw the little capacitors, components, etc shine, so i knew it was a reflow point.
I clean, and tested... voila! worked.
So the problem was clear to me. Cold solder join, BUT, i realized that using Fast charge made a lot of heat on the IC (PM8150b), so i cut a little bit of copper and put it over the IC with some thermal grizzly that i had around. So the heat would transfer mor efficiently onto the screen.
That solved the problem completely and it was more than two years ago since that fix.
I still recommend NOT USE fast charge, so the IC doesn't generate any heat, with fast charge it heated a lot, with regular 5V charge, it doesn't. and is better for the battery anyway.
von Leon Andres Rojas Martinez
Here is a pic of IC.
https://lh3.googleusercontent.com/3-p9po...
von Leon Andres Rojas Martinez