How to check regulator:
Attach multi-meter testing pen to both end of regulator, measure 12v while main power supply to MCU board.
Replace it if the values lower than 12v.

How to check transistor:
Attach multi-meter’s testing pen to the 1st & 5th and 2nd & 5th pin of transistor, measure the voltage while main power supply to MCU board. Replace it if the values lower than 12v and 5V.