| 摘要 |
<p>PURPOSE:To prevent the unlocking of a cylinder revolution follow-up control by impressing a ramp voltage of a steep grade to reduce the loss time before a reel motor starts to rotate and changing it over to a ramp voltage of a gentle grade after the reel motor starts to rotate. CONSTITUTION:An output e0 of a light receiving element for a photodetector 19 of a reel base rotation detecting means 8 in a reel motor starting means is alternately changed in synchronization with the rotation of an aluminum foil 18 during the rotation of a reel base, and this signal is received by an edge detecting circuit 20 to detect a change point of the output e0 of the photodetector 19, and hence a reel base rotation commencement detecting signal e1 is outputted. Then, simultaneously with the commencement of a search, the reel motor 6 is driven by the ramp voltage of a steep grade, and after the reel motor 6 is started to rotate, the ramp voltage is changed over to that of a gentle grade, and not only, of course, when a tape speed reaches a prescribed speed but also even when the tape speed does not reach the prescribed speed in spite of the arrival of the ramp voltage at the max. value for control, these cases are detected to close a servo operation due to a high speed tape traveling control. By this method, a cylinder revolution follow-up servo is prevented from unlocking at the time of starting the servo.</p> |
