Fostex CR200 Service Manual page 20

CR200
4.2.4 Coarse Grating Adjustment
• Objective
• Symptom when out of adjustment
• Measurement instrument connections Oscilloscope to CN104, Pin-3 (TE) via a low pass filter.
• Disc
• Player state
• Adjustment location
[ Procedures ]
(1) Move the pickup to the position where the grating adjustment slit will be seen with the MANUAL / TRACK SEARCH
FWD or REV keys so that the grating adjustment can be adjusted.
(2) Press the FINALIZE key and the PLAY key in the order to close the focus servo and then spindle servo.
(3) Insert a screwdriver into the grating adjustment slit and adjust the grating to find the null point.
For more details, see next page.
(4) If you slowly turn the screwdriver clockwise from the null point, the amplitude of the wave gradually increases. Then, if
you continue turning the screwdriver, the amplitude of the wave becomes smaller again. Turn the screwdriver
counterclockwise from the null point and set the grating to the first point where the wave amplitude reaches its maximum.
Reference : Fig. 13 shows the relation between the angle of the tracking beam with the track and the waveform.
Return the pickup to more or less midway across disc with the MANUAL / TRACK SEARCH key. Then, press the
(5)
PAUSE key and check that the track number and elapsed time are displayed on the front panel. If they are not displayed
at this time or the elapsed time changes irregularly, check the null point and adjust the grating again.
CN104
(TP1)
Pin 3
(TE)
Pin 4
(AGND)
HEAD BOARD
ASSY
20
To align the tracking error generation laser beam spots to the optimum angle on
the track.
Does not start playing, track search is impossible, tracks are skipped.
(HEAD BOARD assy) See Fig. 14 below.
GND probe can be connected to CN104, Pin-4 (AGND).
[ Settings ]: 50 mV/div., 5 mS/div., DC mode
TCD-785
Test mode, focus and spindle servos: closed, tracking servo: open.
Grating adjustment screw in the slit
LPF
(10 : 1)
15k
0.001
F
Fig. 3
Grating
adjustment
screw
Fig. 12
Small
screwdriver