For older models without internet connectivity, you can contact Hisense support directly to request a firmware link or a USB stick with the update. 2. Locating Multi-Part RAR Files
Sites such as Lcd-Led TV Firmwares often host specific mainboard files like the RSAG7.820.7918 .
Visit the Hisense Firmware Download page and enter your TV's Serial Number to see available updates.
Official firmware is the safest option to avoid corrupting your TV's mainboard.