[How-To] bootloader-unlock your Lumia 800 and flash a custom rom

Dear XDA community,

everyday i'm reading new questions from users, how they have to unlock their Lumia 800 and how they can flash custom roms onto it...
So i decided to make this how-to-thread.

I'll keep this post updated as an overview:
post 2: Bootloader unlock DLOAD Lumia 800 to Qualcomm
post 3: Backup and flash your L800 with Ubuntu, flash in Windows using dewe's Lumia Downloader 0.5
post 4: How-To use USB-Video-Out

So please, guys, read this thread, and if you don't understand, feel free to ask. :good:

Bootloader unlock DLOAD Lumia 800 to Qualcomm

If you want to flash a custom rom, you need to have a Lumia 800 with qualcomm bootloader.

But it's a difficult way to make your DLOAD Lumia 800 to Qualcomm:

You need two main things:
1. You need ATF flasher box
2. You need good soldering skills or the special atf cables from gpg industries

Here's a tutorial to SIM-Unlock a Lumia 800: How-To SIM-Unlock your Lumia 800 - gsmhosting.com
This is almost the same procedure for "bootloader-unlocking" your Lumia 800.
You just do not need to click SP-Unlock, you need to click "boot repair" (and select qualcomm, of course).

Here's the thread of the special cables: No more soldering for lumia 610,710,800,900 easiest osbl swap ever
These cables do not require you to solder your device. You only need to open up your phone and connect it to the cable and your ATF Box.

So, if you don't want, or can't buy such a box, check for a local phone repair shop in your town/city. If they have ATF, i'm sure they can do this for you for a small amount.

Hope this helps.

Flash your custom rom using dewe's Lumia Downloader 0.5

Dewe's Nokia Lumia Downloader 0.5

I attached the Nokia Lumia Downloader 0.5 for flashing your Lumia 800 easily in Windows.
Thx to dewe for his great work!

This requires your Lumia 800 to have the qualcomm bootloader!!


First: make a backup of ALL 9 partitions of the phone!
This might really save your ass Id did save mine more than once :good:

1. Install Ubuntu to your computer, or use Ubuntu-Live-CD

2. put phone into "Qualcomm Mode" by pressing VOL UP + POWER and connect it to your pc

3. check with how your phone appears in ubuntu

4. backup your partitions using this:
where the X is your special letter, mostly it's b, c, or d.
if = your input file
of = your output file
And this might take up to 2 hours.

Restoring your backups is the exact opposit.


second: you can now flash your Lumia 800.
because you're already in Ubuntu, you can flash it using:
You MUST flash the os-new.nb file to partition 9!!!



Or you can use attached Nokia Lumia Downloader on Windows.

1. Connect your phone in "qualcomm mode"
2. open the Tool with admin rights in Windows
3. Klick "download" and select os-new.nb file

NOTICE: when you connect the phone in "qualcomm mode" in windows, you'll get a message of formatting the drive. DO NOT DO THAT!!!! CLICK CANCEL! If you format, your phone's broken.

Oh, I was about to write that I'm flashing my phone on Windows but then I saw this method below the Ubuntu.
Isn't it better to put the windows method above the ubuntu? I think more ppl use Windows and possibly won't se the windows method as me

Paviano said:

Oh, I was about to write that I'm flashing my phone on Windows but then I saw this method below the Ubuntu.
Isn't it better to put the windows method above the ubuntu? I think more ppl use Windows and possibly won't se the windows method as me

Click to expand...

Click to collapse

Hi, thx for reply, i wrote it this way, because i wanted to point out, that it is really recommended to make a backup.
If i put the windows flashing above, most people will stop reading, and don't make a backup

I think this way, more people read the backup story, so it's their choice if they don't make one