Sony MZ-E30, Руководство по обслуживанию

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8-2. Intermittent Operations of Servo
The focus servo and tracking servo of this unit turn ON and OFF repeatedly during normal playback and operate
intermittently.
To save power, they repeat 1.8 seconds of ON and 2.8 seconds of OFF as shown in the timing chart in Fig. 8-2. along with the
switching of the laser diode to ON/OFF. In the CLV servo, the control is different. When ON, as some time is required for the
servo to stabilize, the disc is rotated continuously in the rough servo mode even when the focus servo and tracking servo are
OFF. When the servo is ON, the focus servo sets the focus based on the focus voltage just before the servo is OFF to operate
the focus servo circuit.
Fig. 8-2. Intermittent Operations of Servo
8-3. Focus Search and Disc Discrimination
Fig. 8-3. Focus Search (Previous Model)
Compared to the current CD discs, as the reflection rate of the MO disc is low (15 to 30%), the difference between the
pseudo reflected light on the disc surface (polycarbonate board surface of the side where signals are read) and the light
reflected from the MO media side is small, making it difficult for the IC to differentiate between the two. As a result, the FOK
signal sometimes becomes “H” according to the light reflected from the disc surface. Thus when the focus is turned ON, focus
is accidentally imposed on the disc surface. Focus search is therefore performed from near the disc (down search) unlike
current CDs to impose focus. (Part A of Fig. 8-3.)
ON
ON ON OFF OFF
OFF
FOCUS SERVO
TRACKING SERVO
CLV SERVO
ON ON ON OFF OFF OFF
LOCK LOCK LOCK
LASER DIODE
Approx.
1.8[s]
Approx.
2.8[s]
ROUGH SERVO ROUGH SERVO ROUGH SERVO
A
A A
B B
ON
TRK-ON
ON
TRK-ON
Y axis shows the focus drive voltage
The top is the disc.