Downloading a random file labeled "T.V56.03" and flashing it to your board is dangerous. If the firmware you download is designed for a Samsung panel, but your TV uses an LG panel, The screen will either show a distorted image, go black, or the backlight will turn on with no picture.
Most T.V56.03 boards do not have a USB port for user upgrades. To change the firmware, you typically need a . t.v56.03 software free download