| 摘要 |
<p>PURPOSE:To obtain quickly stable reproduced pictures after a start mode by giving phase control to a reference signal generator with a head switching signal synchronized with a drum motor in terms of phase for a period during which the drum motor reaches its steady revolving speed by speed control. CONSTITUTION:The revolving speed of a drum motor 13 and then the phase of a trapezoidal wave signal 21 are changed before the motor 13 reaches its steady revolving speed. Then the phase of the reference signal RP is also changed. Thus the constant phase relation is kept between the signals RP and the trapezoidal wave signal LH. When the motor 13 reaches its steady revolving speed, a switch 19 is closed by the switch signal given from a speed control circuit 18. At the same time, a switch 25 is opend. Thus the signal RP is ketp at the phase set immediately before the switch 25 is opened. The phase control signal delivered from a sample holidng circuit 2 is fed back to the motor 13 via the switch 19, an addition amplifier 17 and a motor control circuit 16. Thus the motor 13 undergoes phase control.</p> |
