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6. Focus servo loop gain adjustment
© Objective
To optimize the focus servo loop gain
© Symptom when out | Playback does not start or focus actuator noisy
of adjustment
© Measurement instru- | See Figure 6.
@ Player state
Test mode, play
ment connections
[Settings]
© Adjustment location | VR152 (FCS GAN)
CHI
CH2
20 mV/division
5 mV/division
X-Y mode
[Procedure]
Set the AF generator output to 1.2 kHz and 1 Vp-p.
Press the MANUAL SEARCH FWD p> or « key to move the pickup to halfway across the disc (R = 35 mm), then
press the TRACK FWD Pi] key, the PLAY [> key, then the PAUSE [I] key in that order to close the corresponding
servos and put the player into play mode.
Adjust VR152 (FCS GAN) so that the Lissajous wave form is symmetrical about the X axis and the Y axis.
5PIN
(FCS IN)
4P
IN
(GND)
Focus Gain Adjustment
Optimum gain
15
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