[Guide] De-branding AT&T Nokia Lumia 635/**820**

[pankaj981]

Description​

This guide will show you how to de-brand your branded AT&T device. At the end of this tutorial your phone will receive updates directly from Microsoft and no longer wait for AT&T to release them.

Warning​

1) All changes made to your phone are pseudo-permanent, pseudo being I haven't tried reverting back to the AT&T firmware, never want to ​

2) This process does need some ROM flashing skills via Nokia Product Support Tool so please proceed with caution (used only if you want to flash another firmware)​

3) I would not be taking responsibility if you accidentally brick your phone so please ask questions before proceeding​

Software Requirements
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​1) AT&T Nokia Lumia 635 or 820 running OS version 8.10.14219. If you are on a lower version please check for updates from AT&T or update using Preview for Developers

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2) Start with a clean software, i.e. reset your phone before proceeding (make sure Preview for Developers is not installed)

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3) Files Needed (download link) ** I do not own these files. They were linked from this thread **​

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• 
  [*=1]SDK 8.1 Lite.zip (*** install this after download ***
  
  [*=1]CustomPFD_0003.xap
  
  [*=1]CustomWPSystem_0500.xap

Hardware Requirements​

1) AT&T Nokia Lumia 635 or 820

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2) microSD card

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3) USB cable​

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Process: Part 1 - Preparation
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1) Hard reset phone using hardware key combination (Reference)

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2) Go through setup process, update all system and preloaded apps

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3) Storage Sense >> phone >> apps+games >> select all >> uninstall all apps

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4) Storage Sense >> Store new apps on my "phone"

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5) Connect phone to PC using USB

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6) PC >> Start Menu >> Programs >> Windows Phone Developer Registration >> Register >> Enter MS Account >> Done >> Close

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7) PC >> Start Menu >> Programs >> Windows Phone Application Deployment 8.1 >> Target = Device; App = "pathoffile\CustomWPSystem_0500.xap" >> Open >> Deploy >> Deploying File >> App deployment complete. >> Close

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8) Verify if CustomWPSystem shows up in app list

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9) PC >> Explorer >> My Computer >> Select Phone >> SD Card >> Documents >> Move CustomPFD_0003.xap here >> Done

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9) Storage Sense >> Store new apps on my "SD Card" >> Done

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10) Store >> Download Preview for Developers >> Let it install >> Don't open after install >> Pin to Start >> Done

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11) Open CustomWPSystem >> Click on red bar "SD Card permissions" >> Select "sd card" >> Press "done" (check mark below) >> red bar turns green

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12) Scroll down under "Modding selected app", select "Select the XAP" >> Phone >> sd card >> Documents >> Select "CustomPFD_0003.xap" >> Apply XAP >> Wait till you see popup "Operation completed!...." >> Done >> Close app​

Process: Part 2 - Registry Edits​

1) Open previously pinned Preview for Developers app >> HKLM >> SYSTEM >> Platform >> DeviceTargetInfo

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2) Edit Registry:

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For Lumia 635: (AT&T Nokia Lumia 635 >> Nokia Lumia 635 US Country Variant Denim ROM)​

PhoneMobileOperatorName >> 000-US >> Write​

PhoneManufacturerModelName >> RM-975_1043 >> Write​

For Lumia 820: (AT&T Nokia Lumia 820 >> Nokia Lumia 820 LTA MX CV Cyan ROM as of 06/02/2015)
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** I haven't tried this personally so proceed with extra caution **
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PhoneMobileOperatorName >> 000-22 >> Write​

PhoneManufacturerModelName >> RM-824_lta_lta1_223 >> Write​

3) Check for Updates >> Install Updates >> Phone is now unbranded​

​** If you want to update to WP 8.1 Update 2 then proceed to this link else continue **​

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4) Reset using "Part 1 - Preparation: step 1)

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5) Start using phone​

Observations​

1) Denim firmware enables graphic equalizer on the 635​

2) Phone can now be flashed to other non-AT&T RM-975s but not AT&T ROM​

3) ** Windows Phone Recovery Tool and Lumia Recovery Tool cannot restore to AT&T firmware **. Use Nokia Product Support Tool to flash other firmware.

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** Or use the method posted below to re-flash the ROM **
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I have a final step to the original procedure. Only do this after you have done a successful unbrand. Use THOR2 (which is conveniently included with the Microsoft Device Recovery tool) to change the product code to match what you did in the registry. In the case of the NAM 4R CV 635 (which is the RM-975_1043 in the example) the product code is 059W4X2. Procedure below:
[INFO]Navigate to the folder where thor2.exe exists i.e. C:\Program Files (x86)\Microsoft Care Suite\Windows Device Recovery Tool and run this command with the phone plugged to USB.
thor2 -mode uefiflash -ffufile "[name of firmware file previously downloaded].ffu" -productcodeupdate 059W4X2 -skip_flash[/INFO]
The -skip_flash flag prevents it from actually flashing the rom to the phone so you don't lose any data.

What this accomplishes is that you can now use the WDRT and it will recognize the phone as the new product code in case you want to use that tool to recover it in the future.
[NOTE]I have verified that this procedure works on RM-877*, RM-975 and RM-915, and doesn't on RM-820. Your mileage may vary.
*the product code change, not the unbranding[/NOTE]
One more really final step for completeness, plug the phone to Nokia Care Suite and print a replacement IMEI/product code/etc barcode sticker. I'll leave that to the diligent to discover.

Thanks to anaheiim for pointing me in the right direction to discover how to do this.

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Note​

1) Please thank the OP, grozaman for posting this method here
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2) This method was used de-brand the AT&T Nokia Lumia 830 RM-983 to the RM-985 variant but it did not work (details). Thanks RumoredNow for volunteering for the experiment!

3) Please thank PepperdotNet for posting about how to reflash the unbranded ROM back to the device
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Useful Links

Nokia ROM Flashing Video [WindowsCentral]​

Nokia/Microsoft ROM Flashing Instructions [xda-developers]

Nokia Product Codes [gsmhosting]

Installing Windows Phone 8.1 Update 2 on Lumia Devices ** [WindowsCentral]

Windows Phone Basics [Microsoft]



Post below if you have any questions.
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[advant]

grozaman and pankaj981, Thanks a bunch for this procedure. I followed the steps exactly as described and was successfully able to debrand my ATT Lumia 635.

 

[UNIX based]

How long is the Windows Developer Registration suppose to take mines stuck on Trying to detect a windows phone connect to the computer

 

[UNIX based]

Forget what i said right here lol

 

[Li_meme_ca]

I updated my Lumia 635 using Preview for Developers and could only get version 8.10.12400.899. How can I get 8.10.14219? Before this I was stuck at 8.10.10xxx.

 

[pankaj981]

I updated my Lumia 635 using Preview for Developers and could only get version 8.10.12400.899. How can I get 8.10.14219? Before this I was stuck at 8.10.10xxx.

Check your preview for developers, it might have unenrolled you after the update. Enroll again and check for updates. It should take you to 14219 eventually

 

[UNIX based]

I was having the same problem were it wont update because of an error. factory reset fixed that problem

 

[Elitewolf]

thanks for this i'll try it one day.

 

[Don Geronimo]

If my 635 is still carrier locked to AT&T, will it be possible to carrier unlock the phone after the debranding, or will I have to unlock it first?

 

[youngsailor]

thank you. this works in my 820. But now it is only in "cyan". To get a "denim" shall I flash it with another firmware? if so, which one would you recommend?

 

[UNIX based]

thank you. this works in my 820. But now it is only in "cyan". To get a "denim" shall I flash it with another firmware? if so, which one would you recommend?

Uncheck developer preview in the app.

 

[Li_meme_ca]

Check your preview for developers, it might have unenrolled you after the update. Enroll again and check for updates. It should take you to 14219 eventually

Thanks. It worked but only after I did a factory reset. Before the reset, it could not check for updates. "error 80072f8f".

Now I am on update 14219 and am ready to debrand my Lumia 635. My device is unlocked; will it stay unlocked after bebranding? I believe it will but better make sure!
Also, sorry if it's a stupid request but I am not clear about step 7 and step 1 of part 2. Could someone expand it so I know what to see/do when I have started the process. I am sure most people on this forum understand what you mean but I am a noob....

 

[pankaj981]

Now I am on update 14219 and am ready to debrand my Lumia 635. My device is unlocked; will it stay unlocked after bebranding? I believe it will but better make sure!

If my 635 is still carrier locked to AT&T, will it be possible to carrier unlock the phone after the debranding, or will I have to unlock it first?

Yes, unlocking is tied to IMEI and not the firmware...you may loose warranty though so please read carefully to avoid a situation

thank you. this works in my 820. But now it is only in "cyan". To get a "denim" shall I flash it with another firmware? if so, which one would you recommend?

If you are on AT&T then please read the guide, mind you the solution is untried on the AT&T 820 so please proceed with caution. If you are not on AT&T then post additional details about your phone, it might be actually easier otherwise

Also, sorry if it's a stupid request but I am not clear about step 7. Could someone expand it so I know what to see/do when I have started the process. I am sure most people on this forum understand what you mean but I am a noob....

See software requirement, Step 3). I would suggest doing this only if you are comfortable enough in fiddling with your phone ROM and registry (this can be dangerous) which looks like you aren't

 

[Li_meme_ca]

I would suggest doing this only if you are comfortable enough in fiddling with your phone ROM and registry (this can be dangerous) which looks like you aren't

Agreed. Thanks for the warning.

I won't proceed until I see the steps in a video. Anyone kind enough to upload a video if you are performing this? Thanks.

 

[rhapdog]

I'd really love to try this with my AT&T 635. How much time would you estimate this will take from start to finish? Would I be able to pull this off within 4 hours time or less, total, with all the resets?

Also, if I want to "rebrand" AND update to WP 8.1 Update 2, do I have to completely repeat all the steps again, starting with the reset after de-branding? Or while I'm at that point, can I edit the registry in Part 2 of the Update 2 instructions and then reset?

If I do the re-brand AND the update to GDR2, then how much time should I set aside for me to get it all finished? 2 hours? 4 hours? more?

 

[pankaj981]

Well from start to finish on a freshly reset'd device takes less then 20 minutes to debrand and about 20 mins to install Update 2. Majority of the time is taken by the backup step so depending on how much data your phone has to backup during the update will really decide the total time.

 

[Li_meme_ca]

I'd really love to try this with my AT&T 635. How much time would you estimate this will take from start to finish? Would I be able to pull this off within 4 hours time or less, total, with all the resets?

Please make a video as you go along....for the noobs

 

[youngsailor]

Uncheck developer preview in the app.

It doesn't help. I guess non rm-824 has denim update yet.

 

[youngsailor]

If you are on AT&T then please read the guide, mind you the solution is untried on the AT&T 820 so please proceed with caution. If you are not on AT&T then post additional details about your phone, it might be actually easier otherwise

yes, mine is from ATT. your method works. but there is no new update on this debranded channel as well. also I tried to reset the phone and it returned back to ATT.

 

[djeire84]

I went from Vodafone Ireland to Three ireland and now I'm totally debranded lol. Its great now I can get direct updates and such instead of waiting on any one mobile carrier to release them. Its,great the only downside is you have to wait two days initially to get the phone IMEI unlocked but after that its plain sailing. I have gotten update 2 also by debranding.