Fostex CR200 Service Manual page 38

CR200
4.3.22 Tracking Servo Loop Gain Adjustment
• Objective
• Symptom when out of adjustment
• Measurement instrument connections Oscilliscope CH1 to CN204, Pin-3 (TRKIN) via 100k½ resistor
• Disc
• Player state
• Adjustment location
[ Procedures ]
(1) Set the AF generator output to 1.2kHz and 2Vp-p.
(2)
Move the pickup to midway across the disc (R = 35mm) with the MANUAL / TRACK SEARCH FWD or REV keys.
(3)
Press the FINALIZE key, the PLAY key and the PAUSE key in the order to close the respective servos and put the player
into play mode.
(4) Adjust VR202 (TE. GAIN) so that the lissajous waveform is symmetrical about X axis and the Y axis.
Higher gain
38
To optimize the tracking servo loop gain.
The unit does not start, during searches the acutuator is noisy, or tracks are skipped.
Oscilloscope CH2 to CN204, Pin-2 (TRKER)
(SERVO UCOM BOARD assy) See Fig.24 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
VR202 (TE. GAIN) (SERVO UCOM BOARD assy)
CN204
(TP201)
100k
Pin 3 (TRKIN)
Pin 4 (AGND)
1.2kHz
2Vp-p
(10:1)
Pin 2 (TRKER)
39k
0.001 F
Low pass filter
Optimum gain
(10:1)
X Y
Fig. 7
Fig. 25
Lower gain