(C) Focus Servo Loop Gain Adjustment
Connection point
Settings
State
Adjustment Location
U1 (KA9220C)
Pin 57 (R11)
Pin 56 (R12)
See fig 3
1.
Oscilloscope Probe: x 10
2.
Oscilloscope setting
CH1: 20mV/division
CH2: 10mV/division
Remark: X-Y mode
Play State
Adjustment VR3
i.
Set the frequency generator output to 1KHz and 100mv.
ii.
Press the play key and press skip key to move the pickup to halfway across the disk
(R=35mm).
iii.
Adjustment VR3(focus gain) so that the Lissajous waveform is symmetrical
above the X axis and the Y axis.
Fig. 3
Focus Gain Adjustment
Higher gain
Optimum gain
Lower gain
FL8550
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