Sony BVU-950 - Page 36

FOR TRAINING PURPOSES ONLY
ion 2. DYNAMIC TRACKING
PRELIMINARY.
SUBJECT TO CHANGE
This is because VeSYNC playback is most important in RF signal. This is because of achieving DTV stabilization
and monitor picture stabilization. Thus, wobbling frequency is about 10Hz, which is rather low compared with
previous units.
There are three stages by which the head height is changed during wobbling. At startup, it is changed in units of 1/10
tracks. Then, since the RF level drops as the maximum point is reached, as shown in Fig. 2-8, it drops back to its
original height. When the maximum levels are counted 10 times, the amount of wobbling changed to 1/30 tracks.
Finally, after the 14th repetition, it is changed to 1/90 tracks.
(G2) TRACKING LocUS
BVU-920
Fig. 2-8.
t
i]
Le
A 8
(b) HEAD POSITION
-_—
oe
oe
of...
HEAD
POSITION
——
©
aw
@
RF
LEVEL
—o~
PA
he
oe
oe
1
’ t
} |
a 68
(GC) RF LEVEL
oL--
This
constitutes
basic
DT
control,
which
is
essential
for
correct
functioning
of
bimorph
head
according
to
voltage
which
is
applied
to
it.
However,
depending
on
characteristics
of
elements
from
which
they
are
made,
displacement
of
bimorph
according
to
voltages
applied
to
them
is
also
affected
by
temperature
fluctuations
and
transient
changes
(hysteresis
and
non-linearity),
etc.
920
DT
control
includes
the
following
functions
to
cope
with
these
effects.
4-20