Disclaimer: Firmware flashing carries a risk of permanently damaging the mainboard if performed incorrectly. Always ensure you are using the correct dump for your specific panel and mainboard version.
A very reliable source, though it requires registration to download files [3]. Download dump samsung ua40h4200ar rar
Here is a curated guide and interesting technical context regarding this process. Where to Download (RAR File) Disclaimer: Firmware flashing carries a risk of permanently