[Galaxy Note II Q&A, Help & Troubleshooting] swifter78neo:
I assume you are on stock ROM, kernel, bootloader and recovery, and are rooted.

Basically there are 3 steps you need to perform:

1. Flash a custom recovery.

2. Using the custom recovery, make a nandroid backup.

3. Find the stock modem and flash it onto your phone.

Warning: You could trip the KNOX flag, and if so, your warranty is bust, and thus, the Samsung technical service will not repair your phone once they find it. Find out if you've tripped it, go to download mode (vol down, home and power) then press vol up. knox warranty void = 0 means you haven't tripped it yet, and 1 means you've tripped it. If it's at 1 there's no point worrying about it, you can't untrip it (as of now). If it's at 0 and you care about warranty then read up on how to do stuff without tripping knox.

Warning 2: Steps 1 and 2 are pretty much 99.9% safe. Step 3, flashing stuff, is always capable of bricking your phone and that's why always backup so that you can restore your phone if stuff goes wrong. I always back up my phone before I do something ambitious (flash custom rom/kernel/upgrade to stock newer android version/change system files/attempt deodex etc.)

Step 1: Choose from clockworkmod, Philz Touch (which is reworked from cwm) and TWRP. Personally I use Philz Touch, latest version here and general and specific read ups. Follow the instructions, flash the tar.md5 latest version via odin.

Step 2: Once done, power off phone fully, then boot to recovery (vol up, home and power). Go to 'backup and restore', and choose custom backup to sdcard or to /storage/sdcard1 for external sd. Backup boot, recovery, system, preload, data, and-sec, modem and data/media. Backup efs (IMPORTANT!!) separately and as much as possible make a copy of all these backups on your computer. You can do this in several times if your sd card(s) are running out of space. By default, the backup locations are in sdcard\clockwordmod\backup\ or the same path in ext-sd. These backups are nandroid backups, and can restore your phone to the exact state it was left at if everything is backed up and then restored. (Like disc images for windows)

Step 3:

Find out the build number and match it to the PDA of a stock ROM on sammobile.

Find out the CSC by dialling *#1234# (if it goes to superuser, press the back button).

Pick the correct stock ROM. For Argentina, the links are:

http://www.sammobile.com/firmwares/3/?download=23587

http://www.sammobile.com/firmwares/3/?download=25933

http://www.sammobile.com/firmwares/3/?download=28314

http://www.sammobile.com/firmwares/3/?download=26273

http://www.sammobile.com/firmwares/3/?download=24475

Choose the one where: 1. Your build no. matches the PDA as much as possible.

2. Your CSC matches

3. Your baseband no. matches modem no.

If I'm not wrong, there is a modem.img or modem.tar or .tar.md5 file. tar and tar.md5 can be flashed via odin, choose phone on odin menu (odin3 v3.04). Google on how to convert .img to tar/tarmd5 if so.

Vary step 3 if you want to try different modems.

This is but one method, I saw people suggesting other methods here.

I reckon I've done enough for the thanks button to be pressed :D:D:D

edit: holy sh*t, spent an hour on this!

edit2: dam the 5 mins restriction. that's a bit too long ain't it?

---------- Post added at 11:47 AM ---------- Previous post was at 11:03 AM ----------

Disclaimer: From what little I know after starting my journey at XDA last week.

1. The usual partitions are boot, system, data, recovery, modem, preload, efs, and separately, external sd. Boot contains bootloader (decides to boot to recovery, download mode or normal) and kernel (the middleman which converts input into instructions to the hardware and shows it to you onscreen or otherwise. custom kernels enable option to over/underclock etc.) System contains the system files such as apks for your ROM to work. Data contains user data such that your data and settings are stored/personalised to you. Recovery is the recovery partition where stock/custom recovery are flashed to. This is where your cwmr is. Modem contains the modem files to connect to networks. Preload contains some system apps to my knowledge. EFS contains your phone's IMEI, without which your phone cannot connect to anything iirc.

2. Kernel is in /boot.

3. By hard reset, I think you mean factory reset? If so, it probably wipes only data, cache and dalvik cache. Because the manufacturer assumes you are not rooted and hence have not dabbled with boot, system, recovery etc since you need root to do so. /cache and dalvik can be safely wiped anytime to my knowledge, they just speed up the user experience after the first reboot.

4. Your backups are probably in either /sdcard/clockwordmod/backup or extsd/clockwordmod/backup.

5. Always make a backup before dabbling in something dangerous. Use your common sense or risk bricking your phone without a recovery image. You can delete old backups simply by deleting them in file explorer or through the recovery menu (at least for philz touch recovery, which i use). /recovery does not contain any backups.

See http://www.addictivetips.com/mobile...plained-boot-system-recovery-data-cache-misc/ for more about partitions.

Press thanks if I helped!! :D