| 摘要 |
<p>DRUM SERVO CONTROL ARRANGEMENT A head drum servo control arrangement is provided in a video tape recording and reproducing apparatus, for example, of the helical scan type, for reducing head phase error at the cut-in point on a magnetic tape during an electronic editing operation. A variable delay circuit imparts an adjustable delay to a detecting signal provided in response to rotation of the head drum. A first phase comparator circuit provides a drive control signal in response to a comparison of phases of the delayed detecting signal and a reproduced synch signal picked up from the tape. A second phase comparator circuit provides a phase error signal in response to a comparison of phases of the reproduced synch signal and a synch signal derived from a video signal to be recorded during the editing operation. A phase control setting circuit, for example, an integrator, provides a phase control signal to the variable delay circuit in response to the phase error signal, while an offset circuit feeds back an adjusting signal to a subtracting circuit in advance of the integrator. This offset circuit can include an attenuator provided with the output of a level comparator having inputs respectively receiving the phase control signal and a reference level.</p> |
