Sony BVH-2000, Руководство по эксплуатации и обслуживанию

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(5-5-2. Principle of Arbitrary Playback)
2. Tracking Control
A tracking error will occur if the DT head is simply displaced at
the angle of the video track at the arbitrary playback. This is due
to a phase shift of the track or the linearity of the DT head path
and video track.
In order to safeguard against this tracking error, the bimorph ,
onto which the DT head is mounted, is wobbled at a constant
frequency (720Hz with NTSCIPAL,
700Hz with PAL/SECAM)
in the direction parallel to the recording head gap, and the
tracking error is detected from the amplitude-modulated
playback RF signal.
A strain gauge is adhered to the bimorph leaf to indicate the DT
head movement but, since sawtooth waves for driving the
bimorph indicating the head jump are also included along with
the wobbling signal, the undesirable
components are removed
and filtered out by a subtracter and high -pass filter, and only the
wobbling components are taken out. The wobbling signal which
indicates the head movement is multiplied by the amplitude
modulated RF envelope signal, it passes through the low -pass
and notch filters, and it is detected as the tracking error
information. The detected tracking error information is returned
to the drive signal and the track is traced.
Recorded Track
Head Trace without
Tracking correction.
(Head off-track + Wobbling)
(a) When the relation between the recorded track and
head trace are not phase.
TRACK CURVE~___ _ __ -~----~
DT
HEAD
Head Trace with
Track ing Correction
(Head off-track
+
Wobbling)
PB RF SIGNAL .
(b) When the DT head traces a recorded track.
DYNAMIC TRACKING SYSTEM
5-5-2
BV H-2000 (U /C) IPS/PM
BVH-2180(U/C)/PS/PM