Here is a thread from another bricked Xperia J... Perhaps some of the steps listed here can help.
>Sony Xperia Miro, Tipo (Dual), J, EXperia Miro, Tipo (Dual), J, E> Q&A, Help & Troubleshooting>[HELP]Xperia J BRICK
If that doesn't help, you would need to post in your devices Q&A section, so the people that know that device can help you....
>Sony Xperia Miro, Tipo (Dual), J, EXperia Miro, Tipo (Dual), J, E> Q&A, Help & Troubleshooting
---------- Post added at 10:01 PM ---------- Previous post was at 09:53 PM ----------
Also... I've read the 3 red blinks means battery is dead.
Try charging it an hour, maybe with a completely different cable and charger.... To be sure that isn't what it is. And pull the battery and reinsert it also.
Just some thoughts.
If not... See the first thread I linked, and if not, post your issue in the second link. 👍