1. Xpress0705's Avatar
    Hi.

    I have an AT&T Lumia 925 that is still stuck on the Cyan firmware thanks their awesome firmware deployment. I would like to debrand the phone to a generic firmware so I can update it to Denim and later W10m.

    Can anyone please link the easiest tutorial for doing so? I mean is there a specific one for Lumia 925?

    I am a newbie concerning the flashing process and my PC is on Windows 10.

    Thanks and best regards.
    10-23-2015 02:01 PM
  2. pankaj981's Avatar
    Unfortunately there isn't an easy way to achieve it. There is a theory that this might work so I am going to put it out there just in case you want to experiment.

    So apparently, the firmware on the AT&T 925 can be debranded but for that you would need to first interop unlock the device and tinker with the registry and trick Microsoft's servers to download and install a different branded firmware (refer to this thread for proof, and it works!). Now to easiest way to interop unlock a 925 is to (this might sound cumbersome) first install WM10, then enable developer mode and install WP Root Tools (refer to this link), then click unlock all capabilities. Then install a registry editor and edit the following strings.

    HKLM >> SYSTEM >> Platform >> DeviceTargetInfo >> PhoneMobileOperatorName >> 000-22 >> Write
    HKLM >> SYSTEM >> Platform >> DeviceTargetInfo >> PhoneManufacturerModelName >> RM-893_lta_lta_204 >> Write

    It should start downloading the unbranded LTA Denim firmware and eventually install. Going forward you can always use Nokia Product Support Tool to flash the unbranded LTA firmware again. To revert back you'll have to use Lumia Software Recovery Tool.

    EMitchell and Xpress0705 like this.
    10-23-2015 07:34 PM
  3. Xpress0705's Avatar
    Thanks for replying.

    I do not want to take risks tinkering with the registry cause am a total newbie with the flashing process. I heard that many people are not able to downgrade once on W10m? I found this post from 2013 : Product Codes For Lumia 925 (unable to post the link) and it appears to be easier. Can you confirm whether this works? Also can you give me more detailed instructions please on how to proceed should I follow the route you showed and what do I need?

    I would like to put this firmware "RM-892 VAR GB CV BLACK 059S916 ( UNBRANDED )" instead of the AT&T one.

    Thanks and best regards.
    10-25-2015 01:40 PM
  4. pankaj981's Avatar
    The AT&T Lumia 925 cannot be unbranded due to AT&T locking its ROM. You can try checking xda-developers but it won't help. Good luck!
    Xpress0705 likes this.
    10-26-2015 12:04 AM
  5. ea3dfx's Avatar
    If you don't want to take a risk of registry editing, you should be able to update ATT lumia 925 to Denim using Windows Insider trick.

    Actually, I think the registry editing is pretty safe if you followed the instruction.
    Xpress0705 likes this.
    10-26-2015 02:08 AM
  6. Xpress0705's Avatar
    Hi.

    Thanks for replying.

    If I use the method of editing the registry, will I be able to debrand the Lumia 925 using what you said above? My phone is already unlocked and I just want to debrand it to "RM-892 VAR GB CV BLACK 059S916 ( UNBRANDED )" . Is this possible? Or do I have to use the Windows Insider trick to get the latest firmware update?

    Thanks.
    11-01-2015 01:40 PM
  7. pankaj981's Avatar
    If you don't want to take a risk of registry editing, you should be able to update ATT lumia 925 to Denim using Windows Insider trick.
    Denim = WP 8.1 Update 1 (in some cases Update 2) + firmware
    Windows Insider = WM10
    Preview for Developers = WP 8.1 Update 1



    Hi.

    Thanks for replying.

    If I use the method of editing the registry, will I be able to debrand the Lumia 925 using what you said above? My phone is already unlocked and I just want to debrand it to "RM-892 VAR GB CV BLACK 059S916 ( UNBRANDED )" . Is this possible? Or do I have to use the Windows Insider trick to get the latest firmware update?

    Thanks.
    From experience, the ubranding only works across similar variants, meaning it MAY NOT work from an AT&T RM-893 to RM-892
    11-02-2015 06:39 PM
  8. ea3dfx's Avatar
    Enrolling into Insider fast ring could push two updates over the phone - the first one is Denim, the second is WM10. Uninstalling the insider app during downloading the first update, the OS will end into Denim (WP 8.1 Update 1).
    I know it is not the full denim, as the firmware wont be updated.
    11-02-2015 09:20 PM
  9. pankaj981's Avatar
    Enrolling into Insider fast ring could push two updates over the phone - the first one is Denim, the second is WM10. Uninstalling the insider app during downloading the first update, the OS will end into Denim (WP 8.1 Update 1).
    I know it is not the full denim, as the firmware wont be updated.
    Does not work for all devices. It downloads the WM10 latest OS build and the Lumia Denim firmware. It's a risky move, especially when one does not want to get WM10.
    11-03-2015 09:26 AM
  10. ea3dfx's Avatar
    Does not work for all devices. It downloads the WM10 latest OS build and the Lumia Denim firmware. It's a risky move, especially when one does not want to get WM10.
    I heard this trick didn't work sometimes. I tried it with my 925 two weeks ago and it worked fine. Even it was loaded with WM10, I guess OS could be rolled back with recovery tool.
    11-03-2015 11:00 AM
  11. pankaj981's Avatar
    I heard this trick didn't work sometimes. I tried it with my 925 two weeks ago and it worked fine. Even it was loaded with WM10, I guess OS could be rolled back with recovery tool.
    It does not rollback the OS only but the last firmware + OS revision. Preview for Developers is the only option for getting the latest WP8.x OS updates
    11-03-2015 02:37 PM
  12. Xpress0705's Avatar
    Hi.

    Thanks for clarifying certain things. If I want to get Denim only without unbranding, will the Preview for Developers get me atleast part of Denim? Second, when the RTM version of W10M releases next year, will using the Windows Insider app update the phone to a stable release of Windows 10 Mobile?

    Thanks and best regards.
    11-15-2015 02:43 AM
  13. pankaj981's Avatar
    Yes, Preview for Developers should get you to WP 8.1 Update 1 (os 14219). The stable release for WM10 would be pushed out this week (hopefully) via Windows Insider.
    Xpress0705 likes this.
    11-15-2015 10:56 AM
  14. Xpress0705's Avatar
    Thanks you.

    I am going to go this route as it seems to be easier for me. Preview for Developers to get atleast part of Denim and insider to get W10M next year. So I don't see the necessity to debrand the phone now. The main reason being from what I heard that without Denim, the phone would not get updated to W10M!

    Thanks and best regards.
    11-17-2015 02:15 PM

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