Abstract: Described herein is a rotary head cylinder assembly including a fixed lower cylinder for guiding travel of a magnetic tape, an upper cylinder rotatably mounted on the lower cylinder and provided with a number of magnetic heads, and a circuit board fixedly mounted on the upper cylinder and supporting thereon amplifiers in positions in close proximity to the respective magnetic heads. The circuit board is provided with notched portions at the outer periphery to permit direct access to screws for adjusting the height of the magnetic heads as well as to holes for adjusting the position of the magnetic heads from above the top side of the cylinder, while preventing interference by undesirable signals.

Abstract: AE signals due to a crack developed in a metal test object are detected by a number of AE sensors mounted on the metal test object. Based on time differences between the signals from the respective AE sensors, crack source points are determined. Then, based on the crack source points, a crack source plane is determined. The crack source plane is divided into a number of areas and a point of maximum number of crack source points in each of the areas is determined. Based on the points of maximum number of crack source points in the respective areas, a shape of the crack in the test object is determined.