I have a xperia J (ST26i) phone and it is hard bricked. 
It does not start,boot vibrate or charge at all . Just notification blinks red led 3 times when power button is pressed. Apart from this there is no response at all. 
I tried with new battery to rule out battery problem but no affect, charged for 6 hours but no affect, sony service center guys says motherboard needs to be changed 
I went to local delhi shops and they said riff does not support ST26i yet for JTAG . Can you guys please help ?