Firmware updates often perform a factory reset or partition reformatting. Back up:
The TP.SK518D.PB802 Go to product viewer dialog for this item. tp.sk518d.pb802 software update
If you are not comfortable with the risk, consult a professional TV repair technician who has a hardware programmer (like an RT809H) to backup your current firmware before attempting any update. Firmware updates often perform a factory reset or