Further to a request on the video on YouTube - I have done a little additional digging:

 

"What is the ID of the MCU I there?Also can you teardown the black box containing the transformer?"

 

The micro controller is a Mitsubishi M37410M4HFP:

 

Here it is in person:

 

Mitsubishi M37410M4HFP

Here is the whole PCB close up:

 

Husqvarna Viking 400, Main Board, Rear

And the Front, just for context:

 

Husqvarna Viking 400, Main Board, Front

 

Unfortunately the transformer is potted into the top half of the enclosure:

 

Husqvarna Viking 400, Power supply

But in case you are interested, the PCB attached to the windings has the AC input and switch at the bottom, the output through the ribbon cable, and 2 quick blow fuses adjacent:

 

Husqvarna Viking 400, Power supply PCB