| 摘要 |
PURPOSE:To prevent the deterioration of the S/N of sounds, by controlling the position of a shielding plate having notch parts and provided outside a motor which drives a rotary magnetic head drum in order to obtain the coincidence between the direction where the leak magnetic flux is minimum and the direction of a fixed magnetic head for sound reproduction. CONSTITUTION:A shielding plate 8 is provided at the outer circumference of a motor which drives a rotary magnetic head drum. The plate 8 has three notch part 8b and control parts 8a and flange parts 8c, i.e., both flange parts. When a rotary magnet 9 turns toward an arrow 19, the leak magnetic flux density distribution is shown by a curve 16. A phase advancing region 18 and a lagging region 17 exist to the signals given from a frequency detecting motor of the magnetic drum, and the magnetic flux leakage noise is reduced at the boundary point 20 between the regions 18 and 17. The plate 8 can be turned + or -20 deg., and the coincidence is obtained between the direction where the magnetic noise is eliminated and the direction of a fixed magnetic head for sound reproduction. As a result, the deterioration is avoided for the S/N of sounds. |
