We are all scared of our phone getting bricked. To all those who do not know what Brick means , it is when you Android phone doesn’t respond or function in any way. So its called a brick . Cause that is what it will be good for. And if you manage to brick your new Galaxy S3 , well i don’t need to explain .  There are many ways to unbrick an Android phone. You can find them on XDA forums.  But they are all confusing to understand , we need a step by step procedure for the task. A senior member of XDA forum had got his hands on a bricked repair guide for Galaxy S3.

Given belwo are some off the main steps

– Brief JTAG process for GT-I9300

1) Copying JTAG(bootloader) file to external SD Card, using normal GT-I9300.

2) inserting the SD card to ‘No Power’ phone, and copy the bootloader file to the defective PBA.

3) After downloading bootloader file to the defective phone, enter the download mode with the phone, and download Full S/W.(PIT, PDA, CSC, PHONE files)

Click on this  Official Thread for more detailed steps.

Source: AndroidHeadlines