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2. Grating adjustment
To align the tracking error generation laser beam spots to the optimum angle on the track
Play does not start, track search is impossible, tracks are skipped.
of adjustment
Connect the oscilloscope to TP1, Pin | Player state
Test mode, focus and spindle servos
ment connections
2 (TRK ERR) via a low pass filter.
closed and tracking servo open
(See Figure 2)
[Settings]
50 mV/division
e Adjustment location | Pickup grating adjustment slit
5 ms/division
DC mode
12-cm disc. For Twin-tray CD type,
an 8-cm
disc can
also be used.
(YEDS-7
can
not be used.) For
Multi-play CD type, use the YEDS-7
test disc.
[Procedure]
1.
When adjusting Twin-tray CD type using a 12-cm disc, always remove the disc tray1. (*)
Move the pickup to the outer edge of the disc with the MANUAL SEARCH FWD
)p> or
key so that the grating
adjustment slit is at the outer edge of the disc where it can be adjusted.
Note :
For Multi-play CD type, use the MANUAL SEARCH FWD
> or
key to move the pickup to half-
way across the disc (R = 35 mm).
Press the TRACK FWD )) key, then the PLAY [> key in that order to close the focus servo then the spindle servo.
Insert an ordinary screwdriver into the grating adjustment slit and adjust the grating to find the null point. For more de-
tails, see the next page.
If you slowly turn the screwdriver counterclockwise (clockwise for Multi-play CD type) from the null point, the am-
plitude of the wave gradually increases, then if you continue tuming the screwdriver, the amplitude of the wave be-
comes smaller again. Turn the screwdriver counterclockwise (clockwise for Multi-play CD type) from the null point
and set the grating to the first point where the wave amplitude reaches its maximum,
Reference : Figure 3 shows the relation between the angle of the tracking beam with the track and the waveform.
Note :
The amplitude of the tracking error signal is about 3 Vp-p (when a 39 kQ + 0.001 pF low pass filter is
used). If this amplitude is extremely small (2 Vp-p), then the objective lens may be dirty or the pickup
malfunctioning. If the difference between the amplitude of the error signal at the innermost edge and out-
ermost edge of the disc is more than 10%, the grating is not adjusted to the optimum point, so adjust it
again.
Return the pickup to more or less midway across the disc with the MANUAL SEARCH REV
key, press the
PAUSE []] key and check that the track number and elapsed time are displayed on the front panel. If they are not dis-
played at this time or the elapsed time changes irregularly, check the null point and adjust the grating again.
Single CD type adjustment locations
* : See Page 18.
3
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