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6. Focus Servo Loop Gain Adjustment
@ Objective
To optimize the focus servo loop gain.
Symptom when out of
adjustment
Playback does not start or focus actuator noisy.
@Player state
Test mode, play
@ Measurement instru-
ment connections
See figure 6.
{Settings}
CHL
CH2
20mV/division
5mV/division
X- Y mode
@ Adjustment iocation
| VR152 (FCS. GAN)
@ Disc
YEDS-7
[Procedure]
1. Set the AF generator output to 1.2kHz and | Vp-p.
2, Press the MANUAL SEARCH FWD P> or REV <kikey to move the pickup to halfway across the disc (R=35 mm),
then press the PROGRAM key, the PLAY
PD key, then the PAUSE {0 key in that order to close the corresponding
servos and put the player into play mode.
3. Adjust VR152 (FCS. GAN) so that the Lissajous waveform is symmetrical about the X axis and the Y axis.
Wi
(10:1)
DB
Pin
5 (FCS. IN)
Pin 4 (GND}
Pin 6 (FCS. ERR) [Q
Figure 6
Focus Gain Adjustment
Higher gain
Optimum gain
Lower gain
47
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