mobile

Hi!

I wanted to update my firmware as some recent lollipop roms refused to flash (I was at AOSPA 4.5 I think). So I looked up, what firmware I had and tried to get back to stock somehow.
It turned out that I had a 1.57.112.2 firmware (T-Mobile AT branding) although I bought an unbranded one (so I should have some x.xx.401.x I think). Nevertheless I looked for stock recovery and backup and found some here (1.57.112.2 recovery) and here (1.57.111.2 twrp backup).
After flashing both, I had a stock ROM running and got an OTA offered which I accepted. After the OTA got downloaded completely, the system said, that it couldn't apply this update. I assume this is because it downloaded the german OTA (1.57.111.2 rom) and wanted to apply it on the austrian firmware (1.57.112.2).
So I thought, maybe I can trick you to download the correct ota by making the rom think, it is the austrian one. I therefor patched the following files:
- system/build.prop
- system/customize/AAInfo.txt
- system/customize/MNS/26201_CS.xml
- system/customize/MNS/26201_Telekom.xml
- system/customize/MNS/default.xml
- system/customize/resource/CCInfo.txt

I basically changed every firmware version or sku occurence from 111 to 112 or t mobile de to t mobile at.
To patch these files I edited them on my pc, pushed to sdcard, booted the phone into recovery, mounted /system and /storage/sdcard1 and then moved the files I had on my sdcard into the correct /system directories.

Then I issued to try the OTA once again. But after the htc splash screen, the screen just turns black. I'm not even able to get into hboot/fastboot during this splash screen.
After a few minutes, the phone reboots, thus showing the htc splash screen once again and turning black afterwards.
While the screen is black, I'm not able adb/fastboot into the device. Also the phone doesn't react on pressing some buttons or plugging the power cable.

Do you have some ideas how to get a working base back?
fastboot, recovery, anything?