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LD-V43000
9. GRATING FINE ADJUSTMENT AND TRACKING BALANCE CHECK
• Purpose: To fine adjust the grating
so
that
the
two laser beams for TRKG
(tracking)
servo
are
emitted at
the
optimum track
positions
of
the
disc.
Set
the DC off-set voltage
to
0V of
TRKG Servo.
• Symptoms when incorrectly
adjusted:
Track jumping.
Measurement equipment
& jigs
•
Oscilloscope
• Test disc: GGV1003
• Flat
bladed
8
screwdriver
Adjusting procedure
Measurement
equipment
connecting points
• Osci11oscope:
In
the
FTSB
assembly
CH
I
(X):
Between
TPl-9
(TRKG
ERROR)
and
GND
CH2
(
Y):
TPl-4
(TRKG
A
+
C)
L Play the test disc and search for frame #16,000, then
open the TRKG servo,
2. Connect the X-input (CHI) of the oscilloscope to
TPl-9 (TRKG ERROR) of
the
FTSB assembly and
Y-input
(CH2)
to
TPl-4
(TRKG
A
+C)
respectively.
Sel
the oscilloscope
to
the X-Y mode,
and
observe
t
he
Lissajous
waveform
o
f
the
TRKG
erro
r signal and
TRKG A;- C signal.
3.
Insert the
flat-bladed small screwdriver
into
the grat-
ing
adjustment
hole,
and
fine
adjust
the
grating
so that
the
Y-axis
dimension of
the
Lissajous waveform
becomes
minimum.
(Fig.9
-
1)
Adjustment diagram
Player condition
•
Service
mode:
• P
lay mode
•
Tracking servo loop
open
•
Tilt
servo
OFF
Adjusting points
• Grating adjustment screw
in the pick-up
assembly
At this time, if the
grating
is
rotated excessively and
the optimum point
be.comes
unclear, perform "2.
Grating
Temporary
Adjustment"
again. (Sec page 109)
4. Select the
X-input
(CHI
)
of
the
oscilloscope, and check
that
the positive
(A)
and
negative (B)
amplitudes
of
t he TRKG
error signal
an
equal. (Photo
10)
If
the
sizes
of
the positive and negative amplitude are
different,
pcrfonn
" 4.
Pick-up Tracking and Tangen-
tial
Direction
Inclination
Adjustment"
again.
5.
Close
the TRKG
servo loop
and
check
that the
pic-
t
ure
on
t
he
TV
screen
is
normal.
Oscilloscope
!
@-
~ ,,'
<
----~,__,
j
~
'"1":
'
'
'
'
~--
----
___
J
11
4
lnsertth11screwdriver
to
t heslot
horlr.ontallvfortho ~ .
Fig. 9-1
~
FTSB
1&Hmbly
.,
'tic.
H/i
o:l
CN4
@I
0
Di;i
0
0
c::JO
0
0
0
§ a
~El
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