MT6739 firmware is not a single file but a collection of partitioned images. Standard partitions include:

If the Preloader is corrupted, the device will not respond to button combinations. The MT6739 BROM allows for USB rescue by shorting the "Test Point" (KCOLO) on the motherboard, forcing the SoC into a mode ready to accept a valid Preloader via SP Flash Tool.

: Standard firmware for this chipset includes roughly 24 partitions, such as: