Question Hi everyone! I need some help with a Sony Xperia Z Ultra (C6833) that won’t boot properly. When powered on, the SONY logo appears, then the screen sta

[traianc]

Hi everyone! I need some help with a Sony Xperia Z Ultra (C6833) that won’t boot properly.
When powered on, the SONY logo appears, then the screen stays lit but completely black. I’ve tried flashing the stock Android 5.1.1 firmware (.ftf) using Flashtool, Newflasher and Fastboot Flasher, but couldn’t get it to install fully.


Currently I can access Fastboot Mode (blue LED, Volume UP + USB cable), and the phone is detected as “Sony Fastboot Interface”.
If I try Volume Down, the green LED never shows up — so Flashmode doesn’t work anymore.
It can boot into TWRP (Power + Volume Down), but touch doesn’t work at all, probably an incompatible version.


The phone reacts to Power, vibrates, and the LED lights up, but it’s stuck on the SONY logo screen.
All I want is to reinstall any Android version (stock, LineageOS, anything) just to make it boot again.


Please note: I’m not interested in paid services.
This phone has sentimental value, and I want to fix it myself with guidance from people who truly know these devices.

 

[Laura Knotek]

Unfortunately you probably won't find anyone here who still have that 12 year old device, especially because most members are from the USA which was never a large market for Sony devices. Your best option would be to try at XDA Developers forums.

 

[Golfdriver97]

If the phone won't get past the boot screen, I'm wondering if the battery is so degraded that it can't stay on anymore. It was released in 2013. The battery having gone bad is not that far-fetched.

If the battery has gone bad, and you tried flashing any firmware to it, the flashing process has been corrupted, and as far as I recall, you have a brick (this would be no different if you stopped a flash in mid-process).