I'm not responsible for the damage that you might cause to your tablet while following this tutorial. Do it at your own risk only. Basic Linux knowledge is required. (Altough you might wan't to try to repair the tablet at your own since sending it back to China costs way too much and it can take 1-2 mounths to get you tablet back.)
Things'll you need:
- Soldering iron
- Old telephone card
- Nokia CA-42 cable (serial to usb) (only important if you need serial connection)
- Micro SD card
- Charger of your tablet
- Pc running Ubuntu 12.04
- Usb cable (not that important)
Disassemble the tablet
There's some disassembly videos on youtube. This one shows T30 but the same applies to T20.
Desolder the battery
This is needed to be 100% sure wether the mainboard is powered or not. Just heat up the soldering iron and simple desolder the black wire. Use tweezers because the wire can heat up pretty quick.
Locate the serial pins onboard
You should find these pins on the main board: TX RX GND and SYSBOOT.
Preparing the cable (not important if you don't need serial connection)
Now you should cut your Nokia CA-42 cable in half to get acces to the cables. If you have a geniune Nokia cable than you could just simply solder the appropriate cables to the pins. Do not solder 3.3v to your tablet's main board!
Preparing your PC (skip if you don't need serial connection)
I have used Ubuntu 12.04 but it should work with other linux distributions as well. You'll need to install a program called Minicom. After installing it you'll need to change the serial port setting inside Minicom like this:
- Serial port: /dev/ttyUSB0
- Hardware flow control: off
- Software flow control: off
After that save it as the default configuration. Close Minicom and then reopen it and check whether you have succesfully modified the default settings or not.
Downloading some software
Download the most recent firware available. After downloading extract it and locate the folder "Boot"
Download Linaro Ubuntu:
I have used a preinstalled Linaro Ubuntu img to correctly format the SD card to enable the board to boot U-boot bootloader from the SD card instead of the internal EMMC.
At time of writing this post this is the latest image. Download it and follow the instructions written here to write the image onto your SD card.
After this unplug and reconnect the SD card to your PC and delete all the files on the Fat partition and copy everthing (logo; MLO; u-boot.img; uImage; uImage_recovery) from the T20 Firmware's Boot folder to the SD's empty Fat partition.
Unmount SD card and insert it into your tablet.
Starting the actual recovery
So by now you should have your prepaired SD card in place and the battery desoldered from the main board.
You have to reconnect the screen's connectors.
Short the SYSBOOT pin to GND on your tablet. Hold down Volume + on your tablet while connecting the charger. Now the CWM recovery should come up and use another SD card with the SmarQT20 firmware on it just like normally upating your Android. From CWM select "install from SD card" and after it has finished your tablet should be working just fine again.
Here is a translated version of the chinese CWM.
Being happy and saying thanks to me
I hope this tutorial was clear and easy to follow, if not please let me know. Also if you have questions feel free to ask me.
Edited by PanzerSajt, 15 September 2012 - 10:21 AM.