Triads: The B Diminished Triad - Transforming the B Diminished Triad into the Bb Major Triad

B-D-F is a diminished triad. Both 3rds are minor 3rds and the 5th is a diminished fifth.

To transform B-D-F into a major triad, one of the minor 3rds must be transformed into a major 3rd.

One way is to lower B to B-flat. B flat up to D is a major 3rd. Retain the minor 3rd D-F.