You can download the firmware for the mainboard from several specialized electronics repair repositories. This board is a universal "three-in-one" driver commonly used to repair or upgrade LED and LCD TVs. Download Sources

If you encounter a error after flashing, you may need a different firmware version that matches your specific panel's LVDS voltage and bit rate. Do you know your panel model number (usually found on a sticker on the back of the LCD screen)? tp.vst59s.pb801 zif z48n-d4 tv main board service info

until the LED stops flashing or the TV restarts.

Turn on the power. The standby LED should begin flashing rapidly, indicating the update is in progress.