[Sony Xperia S, Acro S, Ion] jtr165:
It seems on various blogs/sites that there is a pretty big number of LT28at owners hoping for an AT&T rom, which isn't going to happen...I just wanted to make a quick thread of EXACTLY how to simply flash an available stock JB rom onto the LT28AT...without any other information, and i can simply link to it when needed.

This isn't a criticism, but almost every thread i've seen on using flashtool, there is mixed or downright false information on how to get it to work properly. I know its not just for an Ion, but many tutorials tell you to do things that are either incorrect, or otherwise not needed.

So...if you simply want JB on an LT28AT w/ locked boot loader...and want to keep LTE, etc...simply do this: (this is specific to 64bit windows 8, but similar for vista or 7...the only difference is what you need to do for a flashtool driver)

All of this goes with the assumption that you can find the required stuff to do the flash. Searches will quickly link you to the downloads you need. This is more for getting flashtool to work for you the first time...one other note, for all the driver installation stuff...by default, the action center in windows 8 will just give a prompt of a driver installing...that disappears when the action is completed (instead of previous windows versions saying 'your device is now ready to use', etc.)...and no other notifications are given...so in this case, if you're not seeing errors or other problems, you're good to go...just don't unplug anything until the little installation icon disappears...

download the latest version of flashtool (newest version being released in mid June iirc).

use the Ion development page on this site and find one of the multiple stock rom threads, then download the Ion JB version of your choice, as well as the latest .111 AT&T ICS (this may not be needed, but more on that later)

After that is downloaded, make sure your phone is on, go into the settings menu...under connectivity disable the check box for installing pc companion with a usb connection...that is a myth...you DO NOT need to install PC companion, and in fact PC companion will interfere with flashtool depending on autoplay settings in windows. Also, make sure the phone is in MTP mode, and you can also allow USB debugging in developer options...but for simply flashing; the latter isn't completely necessary.

with PC companion set to not install when you plug in the USB cable, plug your phone into your computer with it still ON. Windows will prompt you for 2 different driver installs, depending on your windows Action Center settings. This will install the Ion on your PC as a device with both internal storage and the ext. card accessible...as apposed to just the SD card...

After that installs, unplug the phone, and turn it off. With it completely off, do nothing but plug the phone in again. Another driver will be installed. Allow that to finish, unplug the phone again. I'm not positive as to what this driver does, but i've had better luck getting this out of the way before the next part...

With the phone unplugged and off still, hold the volume key DOWN and plug the phone back into the PC...The LED will turn bright green, and keep holding the volume key until it disappears...this will install the critical 'S1 Boot Driver'. Windows takes a good full minute or so to install this one, but just be patient, it should go fine.

Now install Flashtool from the setup.exe downloaded earlier. Keep track of its install directory, and after it finishes installing, locate the firmware folder and move your firmware ftf files into there...remember that you may need to unzip the firmware before moving it over, depending on the download source.

Now the windows 8 specific stuff. Windows 8 will block unsigned driver installation by default. To get around this, head to the start screen, bring up the charms, click on settings...and at the bottom right; click on Change PC Settings. From this screen, move to 'general' on the left, then scroll to the bottom and enable 'advanced start up'...and hit restart now.

after a reboot, you'll be taken to a screen with 3 options:

Continue

Troubleshoot

Turn-off

choose troubleshoot, then:

Refresh your PC

Reset your PC

Advanced Options

choose advanced options, then:

System Restore

System Image Recovery

Automatic Repair

Command Prompt

Windows Startup settings

choose windows startup settings, and click restart

after the reboot, you'll find a screen of options again, and simply choose 'disable driver signature enforcement'

now you're almost done

back in the flashtool folder, find the drivers folder...open it, and run the driver installer...you'll see a screen with 25 or so different drivers...ONLY ONE is necessary for the flashing an Ion with a stock rom...at the bottom of the driver list, find 'flashmode driver'...install it, wait for the prompt that its an unsigned driver, and click allow.

Now every bit of communication software between your Ion and PC is complete. You do not need to install all those random drivers, despite claims that they are needed.

to flash your JB rom, phone unplugged from PC and OFF. hit the lightning icon in flashtool...then click flashmode...from the next screen select the JB firmware from the list...set flashtool to wipe everything, and exclude nothing, and leave no final verification checked...this is generally regarded as the best way to flash to a totally new firmware version, limiting bugs, etc...then click flash...wait for the files to be prepared by flashtool...

then follow the on screen prompt, but hold volume down while plugging it in...not 'back'; the screen shows some Xperia phone thats 4 years old or something...

Depending on your area, and the JB version you're flashing...you may need to go back through and flash just the baseband from the att ICS you also downloaded...I didn't have to do this, i still have LTE, i just had to set LTE to 'preferred' in the mobile network settings...you also may need to manually enter the APN settings for att, also...I usually had to do this with international ICS firmwares, but it auto-downloaded perfectly with JB...

Sorry for the length, but I'm sure many guys have run into flashtool fighting back pretty hard...and simply not cooperating...if you install everything in the exact order i listed, you should have no problem...it took me installing this on 5 different machines to finally get it to where it works the first time, every time...PC companion seems to be the biggest variable with this...with that running, it'll very often interrupt flashtool and not let the flash kick off properly...