How to flash firmware with no picture after replacing TCON board

My LCD TV suddenly stopped showing any picture, not even the on screen menus. Audio ok, power ok, Backlight working.

1. i checked power (12v and 5V) at various places on the 3 boards and its OK
2. service manual said tcon board is most likely failure
3. installed a new TCON board and downloaded the latest firmware from SOny on usb drive and trying to flash it

I was told to insert the usb drive with TV UNPLUGGED. then PLUG IN TV. firmware should automatically install and indicator light should blink white during the process of perhaps 1/2 hour and then TV would turn on

BUT i dont see indicator light blink. USB stick blinked at first but 45min later, nothing happening. any help would be appreciated !