The mention of "part4.rar" indicates you are likely downloading a multi-part archive. You must download all parts (e.g., part1, part2, part3, and part4) before you can successfully extract the final firmware file.
Press and hold the or Channel+ button on the TV itself (not the remote). Download BRANDT BAB43F5SNA Firmware USB part4 rar
Use a drive formatted to FAT32 for maximum compatibility. The mention of "part4
Do you need help or identifying the correct USB port for the update? How to update the Samsung TV's firmware using a USB drive Download BRANDT BAB43F5SNA Firmware USB part4 rar
Once extracted, the result is typically a .bin or .pkg file (often named MstarUpgrade.bin or upgrade_loader.pkg ), which the TV recognizes as an update package. Installation Steps via USB