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[GUIDE][BOOTLOADER,TWRP, ROOT]Lenovo TAB3 8/TB3-850F

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MotoJunkie01

Senior Member
Apr 2, 2016
2,403
1,213
Corbin
This guide, for the Lenovo Tab 3 8" (TB3-850F), has 3 purposes:

1. Unlocking your bootloader;
2. Installing TWRP custom recovery;
3. Attaining superuser privileges (root) of the stock OS.

NOTE:
I can attest & confirm that this method has worked 100% on at least 7 devices of my own. Please read and re-read the instructions carefully before proceeding. If you follow this tutorial exactly as delineated, you should have no adverse issues in unlocking your bootloader, flashing custom recovery, or achieving systemless root of the stock Android OS.




MENTIONS & THANKS:
Based on XDA Senior Member @Hemphiz's groundbreaking root and custom recovery for this device, I am now revising this thread wth improved step-by-step instructions based on members' feedback and experiences. Thanks @Hemphiz for your research, assimilation of necessary files, and for breaking ground on this tablet. Thanks also for your granting me ownership of the thread. Your contributions are greatly appreciated by many. Thanks to the great @Chainfire for his flashable systemless rooting script. Thanks to @jemmini for compiling TWRP for this tablet. Finally, thanks to the many members who have tested this guide and provided much needed input & user experience.

DISCLAIMER: As always, please be reminded of the risk involved with flashing a custom recovery and/or attempting to attain superuser privileges of your Android OS. I will not be held responsible for devices bricked or otherwise rendered inoperable as a result of this thread. You assume full responsibility for any good or bad which may result from proceeding any further. However, with that having been said, I will provide any and all support possible. Read and follow the foregoing steps thoroughly and carefully prior to proceeding. NOTE: THIS GUIDE IS INTENDED ONLY FOR THE LENOVO TAB 3 8"/TB3-850F.

REQUIREMENTS:

1. Minimal ADB & Fastboot v1.4 (or newer) Windows Installer;
2. Windows PC or laptop (Mac may be used; however this guide is intended for Windows 7 and newer operating systems);
3. Official Lenovo USB Device Driver v1.1.21;
4. TWRP v3.0.1 for the TB3-850F;
5. ADB Driver Installer for Windows;
6. SuperSU v2.82-SR5 flashable zip.

(All files, drivers & utilities for this process are available in the below download link)

DOWNLOAD LINK: https://drive.google.com/folderview?id=1l-YN5aXmjDF3O1bHxFHVIxLKuvd847Q9




INSTRUCTIONS:


1. First and foremost, unlocking the bootloader is necessary. Also, this step is a good place to make some requisite preparations. Power on your Tab 3 and select SETTINGS once booted up. Go to ABOUT DEVICE, find BUILD NUMBER, and tap it 7 or 8 times until DEVELOPER OPTIONS is enabled. In DEVELOPER OPTIONS, tick OEM UNLOCKING and USB DEBUGGING. On your PC, install the Minimal ADB & Fastboot utilities, the ADB Driver Installer, and the Lenovo USB Driver Installer. Connect your Tab 3 to your PC with the supplied (or quality equivalent) OEM charging/syncing cable. Open a command window in your ADB/Fastboot directory, by holding SHIFT and right clicking in the desired path. In the command window, type: adb devices & press RETURN. If your device is connected properly, the command window will display a string of numbers/letters, which represent your device's serial number. If your serial number does not appear in the window, try changing USB ports, change syncing cables, or try reinstalling the ADB Drivers. Once properly connected, type adb reboot bootloader & press RETURN. Your tablet should boot into Fastboot Mode, which will be displayed in white bold letters on your device's display once complete. Once in Fastboot Mode, type fastboot oem unlock & press RETURN. Your device will prompt you to press Volume Up to proceed with unlocking the bootloader, or Volume Down to cancel the process. WARNING: UNLOCKING THE BOOTLOADER AUTOMATICALLY INITIATES A FACTORY DATA RESET. YOU WILL LOSE ANY UNSAVED VIDEOS, MUSIC, PERSONAL FILES, ETC.

2. Now that your bootloader is unlocked, you are ready to flash TWRP. Download the twrp.img file from my link and save it to your PC in the ADB/Fastboot path/directory. Also, save a copy of the file on your device's internal storage or external micro SD card. Since your device underwent a factory data reset, you will again need to enable DEVELOPER OPTIONS & tick OEM UNLOCKING & USB DEBUGGING as you did in Step 1. When you have done this, again open a command window, ensure a proper connecion, & type adb reboot bootloader & press RETURN. Once in Fastboot Mode, type fastboot boot twrp.img & RETURN. EXTREMELY IMPORTANT NOTE: this device's boot image is secured with dm-verity. Leave the /system partition as read-only when prompted by TWRP. Mounting /system as read/write at this point will result in a boot loop. Flashing SuperSU, as outlined in Step 3, will patch dm-verity and fix this.
From the TWRP main menu, select INSTALL, select the image file option in the bottom right of the screen, navigate to the location where you saved twrp.img in device storage or external storage, and commence the installation. Be certain and correctly choose "recovery" when prompted by TWRP. Now select REBOOT, then RECOVERY. Your TWRP custom recovery should now be successfully installed on your device's /recovery partition.

3. Now, it is time to root this tablet. Download & save a copy of the SuperSU v2.82-SR5 zip file to the tablet's internal or external storage. In TWRP main menu, select INSTALL & navigate to the saved SuperSU zip. Commence with installation. Systemless root mode will unpack, modify, repack and flash the patched boot image. Once done, reboot system. Your Android OS should now have full systemless root, and the /system partition may now safely mount as read/write.

TROUBLESHOOTING:

In the event your device becomes stuck in a bootloop, or is otherwise failing to boot into the OS, the following is a link to my stock firmware images thread for this device. NOTE: the following link will be beneficial only if your device successfully boots into Recovery/Fastboot mode. This link provides stock partition images of /boot, /recovery, /logo & /system. Typically, flashing the stock boot & system images will get you up & running again, and will restore the Android OS to stock condition.
https://forum.xda-developers.com/an...o-tab-3-8-tb3-850f-android-6-0-t3593043/page5

In the unfortunate event that you encounter a brick (your device fails to boot into the OS or Recovery Mode), please visit @r&xp's thread on unbricking your device & restoring it to factory stock condition. Members using his thread be sure to thank @r&xp. His collection of necessary files & comprehensive instructions has saved many, many bricked tablets. https://forum.xda-developers.com/android/help/lenovo-tab-3-8-tb3-850f-unbrick-root-t3598727
 
Last edited:

viv_jen

Senior Member
Aug 9, 2011
400
134
Mumbai
What is your software version?
Mine is TB3-850F_160412
i have a pending 51MB update ,do i complete all updates or ignore them and root?

Also whats the procedure to unroot if i want to get the updates later?
 
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Hemphiz

Senior Member
Sep 12, 2015
924
312
Bristol
m.9gag.com
What is your software version?
Mine is TB3-850F_160412
i have a pending 51MB update ,do i complete all updates or ignore them and root?

Also whats the procedure to unroot if i want to get the updates later?
Look for build number. It's usally best to determine things. I'm on TB3-850F_S100030_161209_ROW
I took the latest OTA before flashing twrp else ota will fail due to the recovery being modified. For unroot there's an option in Superssu to unroot. I would personally create a full backup via twrp before rooting, so you can revert to it if you wish
 

Xecsc

Member
Feb 10, 2010
8
1
51
Richmond
doxmon.com
Thanks for the guide!
Everything works but when I reboot into recovery I just get the dead android with no command under him..
I tried two times with same result Fastboot reports twrp flashes ok

Any ideas?

Thanks
 

MotoJunkie01

Senior Member
Apr 2, 2016
2,403
1,213
Corbin
Thanks for the guide!
Everything works but when I reboot into recovery I just get the dead android with no command under him..
I tried two times with same result Fastboot reports twrp flashes ok

Any ideas?

Thanks
Not to hijack the OP's thread but here are my thoughts. The dead Android indicates that TWRP did not successfully flash to your /recovery partition. Sounds like stock recovery is still installed. First, place a copy of twrp.img on your device's internal storage or on an external micro SD. Try this: instead of typing the command "fastboot flash recovery twrp.img", type " fastboot boot twrp.img" (assuming your twrp file is named twrp.img. If it isn't, rename it twrp.img for simplicity purposes). This command will temporarily boot your device into TWRP recovery. From the main menu on TWRP, select INSTALL. In the bottom right of the screen, select the option for "img" files. Navigate to where you stored "twrp.img" and select it. Install it to "RECOVERY" when prompted. Once it flashes, select REBOOT then select RECOVERY. Your device should now successfully boot into TWRP recovery.
 

phreeker

New member
Nov 26, 2014
4
3
Not to hijack the OP's thread but here are my thoughts. The dead Android indicates that TWRP did not successfully flash to your /recovery partition. Sounds like stock recovery is still installed. First, place a copy of twrp.img on your device's internal storage or on an external micro SD. Try this: instead of typing the command "fastboot flash recovery twrp.img", type " fastboot boot twrp.img" (assuming your twrp file is named twrp.img. If it isn't, rename it twrp.img for simplicity purposes). This command will temporarily boot your device into TWRP recovery. From the main menu on TWRP, select INSTALL. In the bottom right of the screen, select the option for "img" files. Navigate to where you stored "twrp.img" and select it. Install it to "RECOVERY" when prompted. Once it flashes, select REBOOT then select RECOVERY. Your device should now successfully boot into TWRP recovery.

I was running into the same issue after flashing twrp.img via fastboot, it kept coming up with no command when booting into recovery. Followed MotoJunkies advice and booted into twrp.img instead of flashing and installed it that way, now my device is rooted. Thank you Hemphiz and MotoJunkie.
 

Xecsc

Member
Feb 10, 2010
8
1
51
Richmond
doxmon.com
Not to hijack the OP's thread but here are my thoughts. The dead Android indicates that TWRP did not successfully flash to your /recovery partition. Sounds like stock recovery is still installed. First, place a copy of twrp.img on your device's internal storage or on an external micro SD. Try this: instead of typing the command "fastboot flash recovery twrp.img", type " fastboot boot twrp.img" (assuming your twrp file is named twrp.img. If it isn't, rename it twrp.img for simplicity purposes). This command will temporarily boot your device into TWRP recovery. From the main menu on TWRP, select INSTALL. In the bottom right of the screen, select the option for "img" files. Navigate to where you stored "twrp.img" and select it. Install it to "RECOVERY" when prompted. Once it flashes, select REBOOT then select RECOVERY. Your device should now successfully boot into TWRP recovery.

Thanks worked perfect!
 
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figgenhoffer

Member
May 25, 2012
8
3
this did not work for me. now my tablet is in boot loop. keeps going to team win. trying to trying to mount storage and then back to the regular boot. over and over.
 

MotoJunkie01

Senior Member
Apr 2, 2016
2,403
1,213
Corbin
this did not work for me. now my tablet is in boot loop. keeps going to team win. trying to trying to mount storage and then back to the regular boot. over and over.
Hmmm. Did you execute "fastboot oem unlock" first to unlock your bootloader? It sounds as though you are saying TWRP installed correct? When you try to boot into the OS, you are getting reverted back to TWRP?
 
Last edited:

MotoJunkie01

Senior Member
Apr 2, 2016
2,403
1,213
Corbin
i did that. i had teamwin recovery. then installed the superuser.zip and it keeps looping
I see. The superuser zip is likely the culprit. Which one did you use? Did you use the one in the link? Here is a link for the stock boot.img for this device. Install it in fastboot mode by typing "fastboot flash boot boot.img". Try booting after flashing the stock boot image and also try reinstalling the boot script.https://drive.google.com/file/d/0B7-zQU1VihD3ZGZBRzU1Nm1PYjA/view?usp=drivesdk
Note: you will need to rename the downloaded file to " boot.img"
 
Last edited:

smouge

New member
Jul 25, 2010
3
0
Thanks for the guide. Tried to do this on the Lenovo TAB3 10 Business, but no success

I can connect using the tools and enter into fast boot

When I flash, it seems successful, but after shutdown, start with power, volume buttons, I don't see the TWRP, but instead a kind of test app

When i use the other method to boot into the twrp, the Lenovo, boots normal, not into TWRP

Any ideas?
 

MotoJunkie01

Senior Member
Apr 2, 2016
2,403
1,213
Corbin
Thanks for the guide. Tried to do this on the Lenovo TAB3 10 Business, but no success

I can connect using the tools and enter into fast boot

When I flash, it seems successful, but after shutdown, start with power, volume buttons, I don't see the TWRP, but instead a kind of test app

When i use the other method to boot into the twrp, the Lenovo, boots normal, not into TWRP

Any ideas?
When you initially connect your Tab3 to PC and open a command window, did you execute both recognition tests? "adb devices" and "fastboot devices"? I am just curious as to whether your device is being recognized by both the fastboot and the adb platforms. Please try this and let me know.
 
Last edited:

smouge

New member
Jul 25, 2010
3
0
This i what I with Lenovo Tab3 10 business

>adb devices
List of devices attached
8HSKCMT4PJIZ9HDZ device

>adb reboot bootloader

>fastboot devices
8HSKCMT4PJIZ9HDZ fastboot

At this moment, on the Lenovo Android you only see a smaal line at the bottom: =>FASTBOOT mode...

The fastboot does nt deisplay errors, but after the following command, the tablet just boots in the normal Android. On the Android device I also saw quickly the message "USB transferring OK" before booting

>fastboot boot twrp.img
downloading 'boot.img'...
OKAY [ 1.192s]
booting...
OKAY [ 0.073s]
finished. total time: 1.269s

---------- Post added at 09:20 AM ---------- Previous post was at 09:03 AM ----------

On the Lenovo TAB3 10 Business I can also do the following:

Holding Vol up + Power when off and then releasing power when you see the Lenovo logo will bring up the following menu:

Select Boot Mode:

[VOLUME_UP to select. VOLUME_DOWN is OK.]
[Recovery Mode]
[Fastboot Mode]
[Normal Boot] <<==


With the recovery mode I see the following:

Android Recovery
Lenovo/LenovoTB3-X70L/TB3-X70L
6.0/MRA58K/TB3-X70L_S000020_170209_ROW
user/release-keys
Use volume up/down and power.

Reboot system now
Reboot to bootloader
Apply update from ADB
Apply update from SD card
Wipe data/factory reset
Wipe cache partition
Backup user data
Restore user data
Root integrity check
Mount /system
View recovery logs
Power off
 

Hemphiz

Senior Member
Sep 12, 2015
924
312
Bristol
m.9gag.com
This i what I with Lenovo Tab3 10 business

>adb devices
List of devices attached
8HSKCMT4PJIZ9HDZ device

>adb reboot bootloader

>fastboot devices
8HSKCMT4PJIZ9HDZ fastboot

At this moment, on the Lenovo Android you only see a smaal line at the bottom: =>FASTBOOT mode...

The fastboot does nt deisplay errors, but after the following command, the tablet just boots in the normal Android. On the Android device I also saw quickly the message "USB transferring OK" before booting

>fastboot boot twrp.img
downloading 'boot.img'...
OKAY [ 1.192s]
booting...
OKAY [ 0.073s]
finished. total time: 1.269s

---------- Post added at 09:20 AM ---------- Previous post was at 09:03 AM ----------

On the Lenovo TAB3 10 Business I can also do the following:

Holding Vol up + Power when off and then releasing power when you see the Lenovo logo will bring up the following menu:

Select Boot Mode:

[VOLUME_UP to select. VOLUME_DOWN is OK.]
[Recovery Mode]
[Fastboot Mode]
[Normal Boot] <<==


With the recovery mode I see the following:

Android Recovery
Lenovo/LenovoTB3-X70L/TB3-X70L
6.0/MRA58K/TB3-X70L_S000020_170209_ROW
user/release-keys
Use volume up/down and power.

Reboot system now
Reboot to bootloader
Apply update from ADB
Apply update from SD card
Wipe data/factory reset
Wipe cache partition
Backup user data
Restore user data
Root integrity check
Mount /system
View recovery logs
Power off
Chances are the twrp isn't compatible with your device. Although the hardware all looks the same. Problem is my knowledge with Android development isn't that great. I simply read in my spare time. The twrp I found for this device on a previous xda thread, but it was more of a Q&A so I made this guide to simplify things for people. I do know that the original twrp was made here http://4pda.ru/forum/index.php?showforum=583
 

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  • 2
    Great news gents (and ladies, if present), I will be posting a build later tonight.
    1
    Gents and Ladies, I just wanted to check in and say hello. I am making decent headway on revamping the LOS 14.1 ROM. While I will release a full changelog when finished, these are a few of the alterations I've made so far.

    • Removed all RIL, telephony, SIM and cellular network related settings from SettingsUI.apk and SettingsProvider.apk, I e., changed Settings interface to reflect WiFi-Only tablet device.
    • Increased haptic response and touch sensitivity on the touchscreen digitizer via build.prop/default.prop.
    • Android security patches up to December 5, 2020 (actively working towards bringing the patch level all the way up to date).
    • Updated all common libraries, dependencies and modules via Maven Central & remote repositories.
    • Converted specific app modules to library modules.
    • Added optional AMOLED black theme (dark mode) system-wide.
    • Updated system components, system apps, services and framework to the most current LineageOS 14.1 source.
    • Updated MediaTek WiFi and Bluetooth drivers to more current versions.
    • Numerous bug fixes and stability improvements.

    I'll wrap it up in a couple of days I think.
    1
    I needed a new device anyway. I have a refurbished 850f en route. The one I got a few months back was used and had considerable wear. The volume rocker was in the mid stages of giving out as well.
    Oh :)

    On filesystem standards and licensing, the subject matter gets rather complex. Keep in mind that, while Android has long supported USB OTG, it has never officially supported NTFS or exFAT.
    I have noticed this whenever I have tried to download a linux iso of 4GB+ on storage using fat32
    Still to this day, the NTFS filesystem is not supported by AOSP., while exFAT is supported only on some newer devices. Certain device manufacturers, such as Samsung, have added such support via their custom Android overlays like Samsung Experience and One UI. Huawei done the same thing with EMUI and more recently with HarmonyOS 2.0. Samsung was also known to add native support by way of firmware implementations on some devices.
    The legal waters on this topic are extremely muddy. It appears that some companies and corporate entities interpret the licensing and fair use guidelines differently, resulting in a vast disparity regarding native support of these filesystems. Some companies will, while others won't entertain the notion. Many Android file explorer apps now include native support for these filesystem standards. MiXplorer is a good example, as well as a file explorer by Paragon Software.


    Good info. In my opinion better file system support is one of those critical things that's just never talked about. Thanks for your work.
    1
    Did they improve anything?
    Seems to be an insignificant difference in board platforms. The (80) variant has the MediaTek mt6735m SoC, while the (81) variant has the MediaTek mt8161p. The kernels on both variants, however, are compiled for the mt6735m. The two platforms are virtually identical in terms of specs.
    I got my new 850F yesterday, so I'm back at it again.
    1
    Seems to be an insignificant difference in board platforms. The (80) variant has the MediaTek mt6735m SoC, while the (81) variant has the MediaTek mt8161p. The kernels on both variants, however, are compiled for the mt6735m. The two platforms are virtually identical in terms of specs.
    I got my new 850F yesterday, so I'm back at it again.
    I haven't visited this thread in a long time, having moved on to a Mi Pad 4 to replace my TB3-850F.

    But it's really cool to see you pick up the baton on this.

    You now know four people with an (81) variant... add me to the list.

    Mine has a manufacturing date of 2017-04-10 on the sticker.

    I look forward to testing your new build!
  • 12
    This guide, for the Lenovo Tab 3 8" (TB3-850F), has 3 purposes:

    1. Unlocking your bootloader;
    2. Installing TWRP custom recovery;
    3. Attaining superuser privileges (root) of the stock OS.

    NOTE:
    I can attest & confirm that this method has worked 100% on at least 7 devices of my own. Please read and re-read the instructions carefully before proceeding. If you follow this tutorial exactly as delineated, you should have no adverse issues in unlocking your bootloader, flashing custom recovery, or achieving systemless root of the stock Android OS.




    MENTIONS & THANKS:
    Based on XDA Senior Member @Hemphiz's groundbreaking root and custom recovery for this device, I am now revising this thread wth improved step-by-step instructions based on members' feedback and experiences. Thanks @Hemphiz for your research, assimilation of necessary files, and for breaking ground on this tablet. Thanks also for your granting me ownership of the thread. Your contributions are greatly appreciated by many. Thanks to the great @Chainfire for his flashable systemless rooting script. Thanks to @jemmini for compiling TWRP for this tablet. Finally, thanks to the many members who have tested this guide and provided much needed input & user experience.

    DISCLAIMER: As always, please be reminded of the risk involved with flashing a custom recovery and/or attempting to attain superuser privileges of your Android OS. I will not be held responsible for devices bricked or otherwise rendered inoperable as a result of this thread. You assume full responsibility for any good or bad which may result from proceeding any further. However, with that having been said, I will provide any and all support possible. Read and follow the foregoing steps thoroughly and carefully prior to proceeding. NOTE: THIS GUIDE IS INTENDED ONLY FOR THE LENOVO TAB 3 8"/TB3-850F.

    REQUIREMENTS:

    1. Minimal ADB & Fastboot v1.4 (or newer) Windows Installer;
    2. Windows PC or laptop (Mac may be used; however this guide is intended for Windows 7 and newer operating systems);
    3. Official Lenovo USB Device Driver v1.1.21;
    4. TWRP v3.0.1 for the TB3-850F;
    5. ADB Driver Installer for Windows;
    6. SuperSU v2.82-SR5 flashable zip.

    (All files, drivers & utilities for this process are available in the below download link)

    DOWNLOAD LINK: https://drive.google.com/folderview?id=1l-YN5aXmjDF3O1bHxFHVIxLKuvd847Q9




    INSTRUCTIONS:


    1. First and foremost, unlocking the bootloader is necessary. Also, this step is a good place to make some requisite preparations. Power on your Tab 3 and select SETTINGS once booted up. Go to ABOUT DEVICE, find BUILD NUMBER, and tap it 7 or 8 times until DEVELOPER OPTIONS is enabled. In DEVELOPER OPTIONS, tick OEM UNLOCKING and USB DEBUGGING. On your PC, install the Minimal ADB & Fastboot utilities, the ADB Driver Installer, and the Lenovo USB Driver Installer. Connect your Tab 3 to your PC with the supplied (or quality equivalent) OEM charging/syncing cable. Open a command window in your ADB/Fastboot directory, by holding SHIFT and right clicking in the desired path. In the command window, type: adb devices & press RETURN. If your device is connected properly, the command window will display a string of numbers/letters, which represent your device's serial number. If your serial number does not appear in the window, try changing USB ports, change syncing cables, or try reinstalling the ADB Drivers. Once properly connected, type adb reboot bootloader & press RETURN. Your tablet should boot into Fastboot Mode, which will be displayed in white bold letters on your device's display once complete. Once in Fastboot Mode, type fastboot oem unlock & press RETURN. Your device will prompt you to press Volume Up to proceed with unlocking the bootloader, or Volume Down to cancel the process. WARNING: UNLOCKING THE BOOTLOADER AUTOMATICALLY INITIATES A FACTORY DATA RESET. YOU WILL LOSE ANY UNSAVED VIDEOS, MUSIC, PERSONAL FILES, ETC.

    2. Now that your bootloader is unlocked, you are ready to flash TWRP. Download the twrp.img file from my link and save it to your PC in the ADB/Fastboot path/directory. Also, save a copy of the file on your device's internal storage or external micro SD card. Since your device underwent a factory data reset, you will again need to enable DEVELOPER OPTIONS & tick OEM UNLOCKING & USB DEBUGGING as you did in Step 1. When you have done this, again open a command window, ensure a proper connecion, & type adb reboot bootloader & press RETURN. Once in Fastboot Mode, type fastboot boot twrp.img & RETURN. EXTREMELY IMPORTANT NOTE: this device's boot image is secured with dm-verity. Leave the /system partition as read-only when prompted by TWRP. Mounting /system as read/write at this point will result in a boot loop. Flashing SuperSU, as outlined in Step 3, will patch dm-verity and fix this.
    From the TWRP main menu, select INSTALL, select the image file option in the bottom right of the screen, navigate to the location where you saved twrp.img in device storage or external storage, and commence the installation. Be certain and correctly choose "recovery" when prompted by TWRP. Now select REBOOT, then RECOVERY. Your TWRP custom recovery should now be successfully installed on your device's /recovery partition.

    3. Now, it is time to root this tablet. Download & save a copy of the SuperSU v2.82-SR5 zip file to the tablet's internal or external storage. In TWRP main menu, select INSTALL & navigate to the saved SuperSU zip. Commence with installation. Systemless root mode will unpack, modify, repack and flash the patched boot image. Once done, reboot system. Your Android OS should now have full systemless root, and the /system partition may now safely mount as read/write.

    TROUBLESHOOTING:

    In the event your device becomes stuck in a bootloop, or is otherwise failing to boot into the OS, the following is a link to my stock firmware images thread for this device. NOTE: the following link will be beneficial only if your device successfully boots into Recovery/Fastboot mode. This link provides stock partition images of /boot, /recovery, /logo & /system. Typically, flashing the stock boot & system images will get you up & running again, and will restore the Android OS to stock condition.
    https://forum.xda-developers.com/an...o-tab-3-8-tb3-850f-android-6-0-t3593043/page5

    In the unfortunate event that you encounter a brick (your device fails to boot into the OS or Recovery Mode), please visit @r&xp's thread on unbricking your device & restoring it to factory stock condition. Members using his thread be sure to thank @r&xp. His collection of necessary files & comprehensive instructions has saved many, many bricked tablets. https://forum.xda-developers.com/android/help/lenovo-tab-3-8-tb3-850f-unbrick-root-t3598727
    5
    News Flash for users of TB3-850F!

    We now have stable LOS14.1 for TB3-850F! :)

    See post above. Regards, PW.

    Alerting:
    @Hemphiz
    @Lister Of Smeg
    @mtpc
    @stonedpsycho
    @fran89
    @r&xp
    @john3voltas
    @Garcy23
    @voland34
    @DeblaGaming
    @sorun343
    @limited_imagination
    4
    Yeah, I'm not sure how I screwed it up but I'm glad it's working. In order to get into adb I tried the method you mentioned of holding the volume+ for 5 seconds and then plugging in the usb cable. From there I used adb to reboot into the bootloader. I tried flashing the boot and recovery images from there, but it didn't seem like they took. So then I used the fastboot boot command with the TWRP image, but it wouldn't let me access the data partition for some reason. I went to reboot and then all hell broke loose and it was just rebooting through TWRP failing with openscript and then rebooting again nonstop. I couldn't manage to shut it off completely even holding the power button for 30 seconds or so. I figured I was screwed, but held the volume up, volume down (and I think power?) at the same time and suddenly it actually launched TWRP. However, it couldn't access the data partition for some reason. I threw the stock boot, recovery, and system images on an SD card and then flashed them all and that finally got it working.

    I've rooted other phones, but I've had hardly any experience with adb. Fortunately I feel like I did learn quite a bit from screwing up, which is always a plus.
    Great work. Sounds like a good learning experience for you also. These devices on a MediaTek platform are a horse of a different color indeed. I've bricked a good handful of these devices through trial & error myself. By the way, please be sure and hit the thanks button on the OP. @Hemphiz done an excellent job initiating TWRP & root for this great budget tablet.
    I am currently working on a stock based 6.0.1 ROM for this device: rooted, deodexed, debloated & zip aligned. I'll add a few baked-in features like Substratum & Viper4Android. Also I'll add a couple of tunable governors & tweaks to the stock kernel. I'm terribly tied up at work, resulting in having to take a couple weeks break from Android, but I should be up & running again in 3 weeks or so.
    Anyway, I'm very glad it worked out for you. Try this to iron out any bugs with booting TWRP. First, save a copy of the twrp.img to your internal storage or external micro SD card. Next, get your device into TWRP. Select INSTALL, then select the flash img option in the bottom right-hand corner. Navigate to the location of your TWRP.img, commence to install and select "RECOVERY" when prompted to do do. Once done, wipe Cache & Dalvik/ART. Reboot system. This should allow smooth booting of TWRP, with no loops or lags.
    4
    my tablet is tab 3-850f_S100030_161209_row

    so i guess it could be possible to root...i am little be afriad to do that...

    this step 6

    #6 Now you need to boot to your custom recovery via the button combo for the device. (imo this tablet is a pain to boot into recovery compared to most devices) power off the phone. Wait a few seconds. Now hold the power button - then while still holding the power button press Volume up and then Volume down. Hold it for about a second then let them all go. If it worked then you will get the usual boot logo followed by the main twrp screen. Swipe to allow it to make modifications. If it boots into the Chinese recovery thing then just turn it off and try again. I would suggest getting an app that allows you to "reboot to recovery" once your all done and rooted. For root. Simply put the "Supersu sr3" zip in the storage of your tablet. Then flash it via twrp. "install - find where you put the zip - flash - reboot system" Done.

    would someone be more specific to explain...i get my tab in boot mode with holding power buton and volume down an up......and in display is simbol of android with mesage no command..its confused me...

    ---------- Post added at 01:45 PM ---------- Previous post was at 01:28 PM ----------

    i found a solution...press power button 2 seconds and quick press once volume up....

    now i am in recovery boot menu...

    so if someone to explain more specific this step 6

    thanx for advices

    regard

    See this post from Lister of Smeg's TB3-850F Thread, re root & recovery for TB3-850F. Note 'To Enter TWRP':

    filedropper.com/tb3850froot (for files)
    Quote:
    Originally Posted by mtpc
    Hey guys, It's me again. I managed to crack down the russian CAPTCHA and downloaded those files, and it just WORKS! I now have full root on my TB3-850f. I wrote down simple HOW-TO:
    [Slightly ammended by Peter Wallace (Original Post #49)]
    1) Copy SuperSU-v2.79-SR1-20161221223537.zip to the tablet
    2) Enable developer and USB debugging
    3) Open cmd (command Window) in folder with ADB and FASTBOOT
    4) Type these commands:adb reboot bootloader
    Then:fastboot oem unlock
    5) Hold down power button and reboot. Repeat 2) and enable OEM UNLOCK
    6) Repeat 3) and type:adb reboot bootloader
    7) then type:fastboot boot recovery.img (must be copied in the same folder as adb.exe and fastboot.exe)
    (Don't flash recovery yet - system will replace stock recovery before you have root)
    8) Use TWRP to install SuperSU. - Now you have ROOT (Systemless) (can update to SR3, etc)
    9) Repeat 3) and type: adb reboot bootloader
    10) Type:fastboot flash recovery recovery.img - Now your new TWRP recovery will be permanent.
    11) Use TWRP to reinstall SuperSU as lost in step 10 - Now you have ROOT (Systemless).

    To Enter TWRP:
    After powering down, press power, wait 1 sec then hold both vol up & down also (all 3 buttons) until vibrates.

    I also uploaded the files here: filedropper.com/tb3850froot

    Peter W:
    Here is link to latest 850f rom:
    http://lenovo-forums.ru/files/file/1549-lenovo-tab3-a8-tb3-850f_s100030_161209_row/
    Which takes you to https://cloud.mail.ru/public/8T5R/RWCkuBz19
    4
    Thanks for the guide!
    Everything works but when I reboot into recovery I just get the dead android with no command under him..
    I tried two times with same result Fastboot reports twrp flashes ok

    Any ideas?

    Thanks
    Not to hijack the OP's thread but here are my thoughts. The dead Android indicates that TWRP did not successfully flash to your /recovery partition. Sounds like stock recovery is still installed. First, place a copy of twrp.img on your device's internal storage or on an external micro SD. Try this: instead of typing the command "fastboot flash recovery twrp.img", type " fastboot boot twrp.img" (assuming your twrp file is named twrp.img. If it isn't, rename it twrp.img for simplicity purposes). This command will temporarily boot your device into TWRP recovery. From the main menu on TWRP, select INSTALL. In the bottom right of the screen, select the option for "img" files. Navigate to where you stored "twrp.img" and select it. Install it to "RECOVERY" when prompted. Once it flashes, select REBOOT then select RECOVERY. Your device should now successfully boot into TWRP recovery.