: For "dead" units, the firmware is usually flashed directly to the SPI Flash chip using a programmer (like a CH341A) and a .bin file extracted from a working board of the same model.
If you are unable to find the exact .rar file for this specific board/panel combination, technicians often use these methods:
board or help you find a for this specific model? Firmware Updates - Artel Video Systems
: General repair information and schematics for the LC420WUN series are often available via technician communities like Elektrotanya .