Pioneer PD-P920M Service Manual page 33

PD-PSs20M
6. Focus Servo Loop Gain Adjustment
@ Objective To optimize the focus servo loop gain.
e@ Symptom when out of
Playback does not start or focus actuator noisy.
adjustment
@ Measurement instru- See figure 6.
ment connections [Settings]
@ Player state Test mode, play
X- Y mode
1. Set the AF generator output to 1.2kHz and | Vp-p.
2. Press the MANUAL/TRACK SEARCH FWD DP / DDI or REV IKK / <<] key to move the pickup to halfway across
the disc (R=35 mm), then press the PROGRAM key, the PLAY/PAUSE [> / 00 key, then the PLAY/PAUSE D> /00
key in that order to close the corresponding servos and put the player into play mode. (Press the "> /00" key
twice.)
3. Adjust VR152 (FCS. GAN) so that the Lissajous waveform is symmetrical about the X axis and the Y axis.
(10:1)
Pin 5 (FCS. IN)
Pin 4 (GND)
Pin 6 (FCS. ERR)
Figure 6
Focus Gain Adjustment
Higher gain
Optimum gain Lower gain
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