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10.4 FOCS OFFSET ADJUSTMENT (VR1)
1. Turn on the power with no disc in the disc table.
2. Adjust VR 1 so that the voltage at TP2 (FOCS error signal)
is OV.
10.5 GRATING COARSE ADJUSTMENT
1. Remove the 3 mounting screws of the PREB assembly.
2. Load and play the test disc. If the grating is greatly out of
adjustment at this time, playback cannot be started if only
the PLAY lamp on the front panel is flashing. In such cases,
perform a coarse adjustment on the grating.
3. Press the
[PLAY]
key.
4. The TRKG servo will open when the spindle accelerates.
(Ref er to '' Adjustment Precautions.'')
5. Press the
[CLEAR]
key of the remote control.
6. Press the [DISPLAY] key of the front panel to display the
frame number on the monitor screen.
7. Move the Pick-up assembly to frame
#
15,000 using the
[SCAN] (
1111 1111
)
key of the remote control.
8. Insert Eccentric Screwdriver I into the grating, as shown
in
the diagram.
PRES
ASSEMBLY
DEMB
ASSEMBLY
Fig. 10-6
Grating adjustment
Note: Inserting Eccentric Screwdriver I.
The grating adjustment hole of the Pick-up assembly cannot
be seen directly when making an adjustment; therefore, when
inserting Eccentric Screwdriver I, it may be difficult to find the
correct position in some cases. There is danger of damaging
the
laser
diode, so please use the following procedure to insert
Eccentric Screwdriver I into the grating adjustment hole.
Procedure
G)
Place
Eccentric Screwdriver I in the
position
shown in
Fig. 10-7(a).
@
From this
position, move Eccentric
Screwdriver
I
along
the surf ace on the right side until
it
contacts the top.
(Fig. 10-7 (b))
@
From that
position,
move Eccentric Screwdriver
I
along the
underside of the top and to
the
left
for
approximately 5mm
until it
enters
the grating adjustment hole. (Fig.
10-
7(c))
0
0
{a)
0
0
{b)
0
{c)
Fig. 10-7
Inserting Eccentric Screwdriver
I
9. Connect an
oscilloscope to TP4
on
the PREB
assembly and
observe
the
tracking error signal.
Use
Eccentric Screwdriver
I to adjust the tracking
so
that amplitude
is
minimum and
the
waveform envelope
is
smooth.
(Photo 10-1)
Photo 10-1 TR KG error
waveform
100mV/div
5mS/div
(loop
open, minimum
amplitude)
From that position, slowly rotate the screwdriver in the direc-
tion shown by
the
arrow in Fig. 10-6 to adjust the grating so
that the amplitude of the
initial
error signal is maximum. (Photo
10-2)
47
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