How can i find the source of a high pitched noise
I do this all the time, bringing back 1970s power supplies back from the dead.

Get yourself about 18in of aquarium tubing.   Stick one end in your ear.  Wave the other end around the board to find the noise source.

Perhaps clean your ears out first.   And perhaps slightly shave off or melt the cut edge of the aquarium tubing, so you don't get 'paper cuts' inside your ear canal.