There are two fuse arrangements for the MCU. For standard North American / 115 VAC applications, there is one 5 amp slow blow fuse on one leg in the fuse holder, with a coiled spring on the other leg. For European / 230 VAC applications, there are two 2.5 amp fuses in the holder.
If your MCU has a European-style fuse arrangement in it, the 2.5 amp fuses will be prone to blowing at 115 volts. Please change to 5 amp fuses.
Also, please confirm that your line voltage is ok, and that the outlets, cords, etc. are properly grounded.
If the MCU already has a 5 amp fuse, and they keep blowing, then the MCU will need to return to the factory.
For both arrangements, the tracker uses 250 V fuses. The size for both arrangements is IEC 60127-2, 5 x 20 mm fuses.
Keywords: fuse, blown fuse, blown, MCU, master control unit, fuse