What is the with the TV (e.g., won't turn on, stuck on logo)?
If it's for a fix, I can try to help you narrow down the best version of this firmware. Download MSD6A638 T8E2 Toshiba 43U7750 170207 zip
Do not turn off the power during the update process. What is the with the TV (e
Fixes system crashes, stuck at Toshiba logo, or reboots, and brings the software back to a working state (e.g., 2017/2018 versions). Important Notes: won't turn on
42.5" Toshiba 43U7750 - Specifications - DisplaySpecifications
Usually, the file is placed on a FAT32 formatted USB drive, which is then plugged into the TV, and the power is cycled while holding the power button or menu button to initiate the loading process (sometimes known as MstarUpgrade.bin or similar).