Fostex CR200 Service Manual page 37

4.3.21 Focus Servo Loop Gain Adjustment
• Objective
• Symptom when out of adjustment
• Measurement instrument connections Oscilliscope CH1 to CN204, Pin-5 (FCSIN) via 100k½ resistor
• Disc
• Player state
• Adjustment location
[ Procedures ]
(1) Set the AF generator output to 1.4kHz and 1Vp-p.
(2) Move the pickup to midway across the disc (R = 35mm) with the MANUAL / TRACK SEARCH FWD or REV keys.
Press the FINALIZE key, the PLAY key and the PAUSE key in the order to close the respective servos and put the player
(3)
into play mode.
(4) Adjust VR201 (FCS. GAIN) so that the lissajous waveform is symmetrical about X axis and the Y axis.
Higher gain
To optimize the focus servo loop gain.
Playback does not start or focus acutuator noisy.
Oscilloscope CH2 to CN204, Pin-6 (FCSER)
(SERVO UCOM BOARD assy) See Fig.23 below.
[ Settings ]
CH1 : 0.1 V/div., X-Y mode
CH2 : 10 mV/div.
GND probe can be connected to CN204, Pin-4 (AGND).
TCD-785
Test mode, play
VR201 (FCS. GAIN) (SERVO UCOM BOARD assy)
CN204
(TP201)
100k
Pin 5 (FCSIN)
Pin 4 (AGND)
1.4kHz
1Vp-p
Pin 6 (FCSER)
(10 : 1)
Fig. 24
Fig. 6
Optimum gain
(10 : 1)
X Y
CR200
Lower gain
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