1. shikhanshu's Avatar
    I bought the AT&T GoPhone Lumia 640 LTE from Best Buy recently. I am located in USA. Got it unlocked from AT&T. Verified it is unlocked by popping in a T-Mobile SIM card and yes, I am able to make calls and use LTE data. All good.

    But I bought this for my dad who is in India. Can anyone comment if this phone will now work with Indian SIM cards like Airtel or BSNL which offer 3G data? (LTE is not yet widespread in India).

    Do I need to "de-brand" to make it work? Or will it just work as it is right now?

    Thanks in advance!
    04-18-2016 03:58 PM
  2. RumoredNow's Avatar
    Carriers in India all seem to rely on UMTS Band 1 (2100 MHz) for 3G/H+.

    GoPhone 640 has the enabled right out of the box.

    DeBrand only if you are worried about your Father not getting updates.
  3. RumoredNow's Avatar
    Carriers in India all seem to rely on UMTS Band 1 (2100 MHz) for 3G/H+.

    GoPhone 640 has the enabled right out of the box.

    DeBrand only if you are worried about your Father not getting updates.
    shikhanshu, libra89 and pankaj981 like this.
    04-18-2016 06:36 PM
  4. pankaj981's Avatar
    It will work in India. You can de-brand it to the LTA Mexico 7R ROM, and get WM10 officially right away.
    shikhanshu, libra89 and RumoredNow like this.
    04-18-2016 10:38 PM
  5. shikhanshu's Avatar
    Thank you for the response! Looks like I don't need to de-brand it since I don't care about WM10 nor does my dad.
    RumoredNow likes this.
    04-19-2016 10:56 AM
  6. pankaj981's Avatar
    Thank you for the response! Looks like I don't need to de-brand it since I don't care about WM10 nor does my dad.
    He won't for now..but all the cool new apps (example Facebook, Messenger w/ calling, Gaana, Saavn, etc.) are being launched on WM10 only. Its better to have him run the latest and greatest right now rather than going through the hassle later.
    RumoredNow likes this.
    04-19-2016 11:30 AM
  7. shikhanshu's Avatar
    He won't for now..but all the cool new apps (example Facebook, Messenger w/ calling, Gaana, Saavn, etc.) are being launched on WM10 only. Its better to have him run the latest and greatest right now rather than going through the hassle later.
    Sure. I meant, AT&T will release Win 10 as OTA someday. And we are not really waiting on it or anything. Plus he is a very light smartphone user and whatever Windows 8.1 apps are available, will be sufficient for him. Thanks for the tip though!
    04-19-2016 11:39 AM
  8. RumoredNow's Avatar
    I concur. At the very least... Go Insider Release Ring. Upgrade and go back to Production. Then do a Software Reset on the phone and it will be fresh W10M for him. WaaS will deliver any updates to the OS even if you don't debrand it.
    pankaj981 likes this.
    04-19-2016 11:41 AM
  9. shikhanshu's Avatar
    I concur. At the very least... Go Insider Release Ring. Upgrade and go back to Production. Then do a Software Reset on the phone and it will be fresh W10M for him. WaaS will deliver any updates to the OS even if you don't debrand it.
    Oh I see. That sounds like a great idea. I can definitely do that. De-branding process seemed quite involved and risky to be honest.

    However, I have tried both Threshold and RedStone builds on this phone in the last couple of weeks. But the battery life has been very less as compared to Windows 8.1 in general. So I used the Device Recovery tool to get back to Windows 8.1

    What are your comments on battery life in the most stable Windows 10 build as compared to Windows 8.1 Denim? All things equal (I mean same settings - location on, double tap to wake etc.; and same apps installed).
    04-19-2016 11:44 AM
  10. RumoredNow's Avatar
    On my 640, I went Release and got 10586.164. I hadn't really been on 8.1 long. I went over to Release within 2 days. However, I did a Reset right after Upgrade and set everything up by hand, no backup restore. I then drove the phone daily for about 3 weeks. No battery problems for me.

    640 is my backup, so I returned to 1520. I haven't driven 10586.218 on the 640, but based on the change with my 1520, I'm not worried about battery.

    Upgrade/Reset/no Backup = pretty smooth IMHO.
    04-19-2016 11:51 AM
  11. shikhanshu's Avatar
    On my 640, I went Release and got 10586.164. I hadn't really been on 8.1 long. I went over to Release within 2 days. However, I did a Reset right after Upgrade and set everything up by hand, no backup restore. I then drove the phone daily for about 3 weeks. No battery problems for me.

    640 is my backup, so I returned to 1520. I haven't driven 10586.218 on the 640, but based on the change with my 1520, I'm not worried about battery.

    Upgrade/Reset/no Backup = pretty smooth IMHO.
    Ok. I have had a marvelous battery life with 8.1 denim so far. Standby (with minimal usage) going up to 4 days. Regular usage (with 6-7 SOT) going up to 2 full days before a recharge is needed.

    I am going to do the "Release ring -> WM10 -> Back to production -> Reset" thing and test out the battery for next week. If it looks good, I will stick to it!

    And you are sure that if I go back to production after taking WM10 from release ring, I would continue to get future WM10 updates from Microsoft? Or will it then again depend on AT&T to get the updates?
    RumoredNow likes this.
    04-19-2016 11:55 AM
  12. pankaj981's Avatar
    I have been using an AT&T 640 (de-branded to AR CV ROM) with 10586.218 and the battery life has been more or less the same as on 8.1 Update 2. I would agree with RumoredNow's suggestion of at least upgrading to 10586.218 through Windows Insider. After he is on the RTM branch he will continue to get updates directly from MS.
    RumoredNow likes this.
    04-19-2016 11:57 AM
  13. RumoredNow's Avatar
    And you are sure that if I go back to production after taking WM10 from release ring, I would continue to get future WM10 updates from Microsoft? Or will it then again depend on AT&T to get the updates?
    That's the new deal. WaaS delivers OS updates without Carrier or OEM wait. Only Firmware updates which could affect the radio stack are held by carriers.
    pankaj981 likes this.
    04-19-2016 11:57 AM
  14. shikhanshu's Avatar
    Thanks both of you for the insight and helpful information. I will ready the phone with WM10 before my trip to India.

    I actually love the Windows phone OS (be it 8.1 or 10). It is well thought out, beautiful and functional. There are some bugs in the updating of apps in Store app. It is not always in sync with what's on my phone, what has been updated, what has not been updated yet and so on. But that's not too much of a big deal. Bigger issues exist in iOS's App Store compared to this.

    And to get awesome hardware and OS for $30? I am just glad Windows phone has not been a hit with general public who are crazy about apples. :D
    RumoredNow likes this.
    04-19-2016 12:01 PM
  15. shikhanshu's Avatar
    It will work in India. You can de-brand it to the LTA Mexico 7R ROM, and get WM10 officially right away.
    I am thinking of taking the plunge and do the de-branding to get official WM10 update (instead of Insider).
    Can you suggest the right ROM to use in India? Is there an India specific ROM? Or should I just go with the LTA Mexico 7R ROM that you suggested? Also, download link will be appreciated :)
    04-22-2016 05:14 PM
  16. pankaj981's Avatar
    Can you suggest the right ROM to use in India? Is there an India specific ROM? Or should I just go with the LTA Mexico 7R ROM that you suggested? Also, download link will be appreciated :)
    India specific RM-1073 ROMs do not exist but the 7R ROM would work just fine. You can download it from here.
    shikhanshu and RumoredNow like this.
    04-22-2016 05:43 PM
  17. shikhanshu's Avatar
    India specific RM-1073 ROMs do not exist but the 7R ROM would work just fine. You can download it from here.
    Thank you! That's what I will use then.
    04-22-2016 05:44 PM
  18. shikhanshu's Avatar
    India specific RM-1073 ROMs do not exist but the 7R ROM would work just fine. You can download it from here.
    Hmm. This website has 3 different variants of firmware for Lumia 640 LTE:
    RM-1072, RM-1073, RM-1074
    And each of them has whole bunch of sub-variants.

    What is the difference? How does one decide what to take? Just curious. Are there any descriptions anywhere?
    04-22-2016 05:49 PM
  19. pankaj981's Avatar
    No there aren't any descriptions but folks familiar with Lumia flashing would probably look at the country codes and figure out the right version. The one for you would be 059X153. RM-1072/74 are regional single-SIM variants and have different hardware-specific network bands.
    RumoredNow likes this.
    04-22-2016 05:55 PM
  20. shikhanshu's Avatar
    No there aren't any descriptions but folks familiar with Lumia flashing would probably look at the country codes and figure out the right version. The one for you would be 059X153. RM-1072/74 are regional single-SIM variants and have different hardware-specific network bands.
    Looking more closely at the firmware versions, AT&T ROM's firmware version seems newer than Mexico CV ROM:
    059X0B8 - RM-1073 VAR NAM US ATT SL = 02177.00000.15184.36016
    059X153 - RM-1073 VAR LTA 7R CV = 02177.00000.15184.36003

    Is it a good idea to go down in the version? Also, if I do switch to 7R ROM, and get Windows 10 OTA sooner, will the firmware version also be upgraded to something newer? I thought carriers make firmwares? Since 7R ROM will be "no carrier" basically, will firmware version always remain that 36003 regardless of what Windows 10 build I am on in the future?
    04-22-2016 11:01 PM
  21. boonesmi's Avatar
    with cv versions you still get firmware updates. the difference is that microsoft handles the firmware updates.

    when dealing with a carrier rom then the carrier handles firmware updates.


    i personally use tmobile rom (i use tmobile as my phone provider), and still waiting for carrier firmware to fix the wifi calling/volte bug.. but if i didn't have tmobile then i would go for a cv varient (probably mexico) and let microsoft handle all firmware and OS updates
    RumoredNow likes this.
    04-22-2016 11:42 PM
  22. shikhanshu's Avatar
    No there aren't any descriptions but folks familiar with Lumia flashing would probably look at the country codes and figure out the right version. The one for you would be 059X153. RM-1072/74 are regional single-SIM variants and have different hardware-specific network bands.
    Hello pankaj981,

    Just one more question and then you can close this thread :)

    To install the Mexico ROM, do I really need to follow these cryptic and risky looking instructions at XDA for "debranding"?
    De-Brand [ATT] Lumia 640 LTE | Windows Phone 8 Development and Hacking

    Or can I just do what Lumiafirmware.com tutorial says:
    http://www.lumiafirmware.com/info

    Thanks!
    04-23-2016 06:01 PM
  23. pankaj981's Avatar
    From what I know, the xda-developers hack is the only method to debrand the AT&T 640.
    RumoredNow likes this.
    04-24-2016 09:55 AM
  24. jitensetia's Avatar
    Hi Pankaj,

    I have bought at&T unlocked phone from USA, and now I want to debrand it to switch to 3G mode (only 4g is available in it as of now). I'm from India and its a LTE single sim version. So which ROM should I go with ?
    04-28-2016 08:36 AM
  25. jitensetia's Avatar
    From what I know, the xda-developers hack is the only method to debrand the AT&T 640.
    Hi Pankaj,

    I have bought at&T unlocked phone from USA, and now I want to debrand it to switch to 3G mode (only 4g is available in it as of now). I'm from India and its a LTE single sim version. So which ROM should I go with ?
    04-29-2016 10:46 PM

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