Sony has released the official Android 4.1.2 Jelly Bean update for Xperia TX LT29i started on March 28, 2013. The new 4.1.2 Jelly Bean firmware build number is 9.1.B.0.411, those who missed this update earlier, you can simply update your Xperia TX using the PC companion software tool for Sony Xperia devices, instructions on how to update your Xperia TX to Android 4.1.2 Jelly Bean can be found at Sony’s official software update support page.
For experienced users, who doesn’t receive this update using the PC companion for some reasons if your Xperia TX has been modified, rooted or installed with custom ROM. You can still manually upgrade using the original stock 9.1.B.0.411 TFT file and Flash tool.
Download the Flash tool and the LT29i_9.1.B.0.411_Global.ftf FTf file, and then just simply follow the Flash tool on-screen instructions to upgrade your Sony Xperia TX to Android 4.1.2 Jelly Bean. Enjoy!