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LD-V4300D
11. FOCUS SERVO LOOP GAIN ADJUSTMENT
• Purpose: To set the loop gain
of
the FOCS (focus) servo to the optimum
value.
• Symptoms when incorrectly adjusted: Play ability grow worse.
Measurement equipment
Measurement equipment
Player condition
&
jigs
connecting points
Adjusting points
•
Oscilloscope
•
Oscilloscope:
In FTSB • Normal
mode::
• VRS
in
the FTSB
assembly
• Test
disc: GGV1003
assembly
•
Still
mode
•
~
oscillator
CHl
(X):
Between • TILT
servo OFF
•
Resistance
(l00kQ)
TPl -5 (FOCS ERR
IN)
with
lOOkO and
GND
CH2
(Y):
TPl -6 (FOCS
ERR
OUT)
Adjusting procedure
I. Play the test disc and search ror
frame
#
15,000.
2. Connect the X and Y terminals
of
the oscilloscope
as
shown in Fig. 11-1, and observe
the
Lissajous's
waveforms.
3.
Adjust VRS so
that the
Lissajous's
wavefonn as
shown in
Photo
13
appears. Photo
12
shows
a
waveform
when the adjustment is incorrect.
Adjustment diagram
Oscilloscope
FTSB
assembly
H11X
~ - - - - - + - - + o C H 2 { ' f
D~
OD
.,
0
0
oo
0
l a § l
Fig.11-1
"--"
AF
oscilletor
2.1
kHz/0.5Vp-
p
0
• Oscilloscope
range:
X-V mode
X: 100mV/div.
DC
input
Y: 20mV/div. DC input
Wavelonn w
hen
in,ufficl,ntly adjusted
Photo 12
Photo
13
11
7
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