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Update Samsung Galaxy S3 to Android 4.3 JB with Unofficial CM 10.2 Test Build ROM

The Samsung Galaxy S3 smartphone has received its own version of CyanogenMod 10.2 Unofficial ROM, which is why you need to use this post if you want to install it on your smartphone. Read all the info that I’ve listed below and you should be able to apply the update in no time without bricking your device.

CyanogenMod team works on the release of their first official take on Android 4.3 JB. It will include several new features and functions that should improve the overall Android experience for CM users. In order to make sure that you successfully update your device with this new ROM, you will first have to take a look at these guidelines:

  • This guide will work exclusively with the Samsung Galaxy S3 model number I9300.
  • Do not attempt to update any other Galaxy S3 variant using the files posted in this article, you will end up bricking the phone.
  • Install the CM 10.2 test build on Galaxy S3 phones that are factory unlocked and rooted.
  • Also, your phone has to run a custom Recovery image such as CWM or TWRP.
  • Before starting the update use the custom Recovery mode to create a full NANDROID backup of the currently SGS3 installed ROM. It will set a restore point for your smartphone and it can be used in case the new ROM doesn’t boot into normal mode.
  • The tutorial will ask you to apply ‘factory reset’ for your device, which means that all installed apps, SMS, Call Logs info and other similar data files will be removed in the process.
  • The factory reset will only wipe the system partition, while the internal and external SD cards won’t be affected by this process.
  • If your Galaxy S3 is currently running a previous CM 10.1.x ROM build, then you can skip the ‘factory reset’ and flash the new ROM over it.
  • NOTE: In case the new Unofficial CM 10.2 Test build doesn’t boot, then you will have to return to the tutorial and apply the ‘factory reset’ step, as that will force the SGS3 to boot into normal mode.
  • If you want to backup SMS and similar other system data files then you need to use these apps for Android: SMS backup & restore | Call Logs backup & restore | APN Settings Backup & Restore.
  • You have to sync your Contacts info with your Gmail account before starting the updating process. This will backup all your saved Contacts data and phone numbers.
  • Enable USB debugging from Developer Options.
  • Read all the instructions in this post and do not skip any of the steps listed in the how-to part of this tutorial.
  • We cannot be blamed in case you brick your device or you lose any important files while you’re attempting to update your smartphone.
  • For any other questions use the comments field.

Since you’ve read all of the above, continue to the next part of this article and learn how to update your smartphone.

How to flash Unofficial CM 10.2 Test build ROM for Samsung Galaxy S3 I9300:

  1.  Download the CM 10.2 test zip file from here.
    > save the file on your PC and don’t unzip its contents.
  2. Download modified Gapps zip for this new ROM from here.
    > do not unzip, save it on your computer.
  3. Connect your Galaxy S3 with your computer using the USB Data cable.
  4. Move the downloaded zip files and place them on your phone’s internal SDcard.
  5. After the files are copied, disconnect the Galaxy S3 from PC.
  6. Power off your phone now.
  7. Boot the device into Custom Recovery mode.
  8. Create a full NANDROID backup of the currently installed ROM:
    > for CWM Recovery: select ‘backup and restore’ option. Confirm this process and get to the next step when done.
    > for TWRP Recovery: press Backup, then confirm that you wish to create the Nandroid backup file.
  9. Next, apply Factory Reset:
    > CWM Recovery: select ‘wipe data/ factory reset’. Confirm.
    > TWRP Recovery: press Wipe button and then press the Factory Reset one. Confirm the process.
    > if your device is already sporting a previous CM 10.1.x build, then you can skip factory reset.
  10. Install the new Unofficial CM 10.2 test build:
    > CWM: select ‘install zip from sdcard’, then you need to select ‘choose zip from sdcard’. Find the CM 10.2 ROM zip and install it.
    > TWRP: press Install, then browse your device’s internal SDcard for the CM 10.2 zip. Confirm that you wish to update your device by sliding the bottom blue button.
  11. Since you’ve installed the ROM, repeat step 10 in order to flash the Gapps zip too.
  12. When all the files have been successfully installed, return to the main Recovery screen.
  13. Reboot your Galaxy S3 now into CM 10.2 Unofficial ROM.
  14. Enter the Google Account info and take control over your device once again.

These were all the steps that you had to take in order to update your device with the latest Unofficial CyanogenMod 10.2 ROM. If the installation doesn’t complete at your first try, then you should keep trying until all the files are flashed successfully. Repeat the tutorial and make sure that the second time you don’t skip any steps listed above.

If your smartphone doesn’t work smoothly with the new CM 10.2 ROM, then you should use the NANDROID backup files created in step 8 to restore it to its previous ROM. For any other questions use the comments field below.

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