Fisher DAC-204 - Page 5

ADJUSTMENT PROCEDURES (continued)
10K oQ47
E
10K 0.047
uD GND Dualtrace
Oscilloscope
10K 0.047 10K 0.047
F
4. Press the F FWD button. The TRACK No. indication is “2”
and the disc begins to rotate. Continue to press the PLAY
button. The unit is rotating in this state with the tracking
servo turned off.
5. Observe the resurge waveform of the waveform indicated on
the oscilloscope and insert the adjustment jig into the
diffraction grid holes to adjust the diffraction grid so that the
phase difference is 180°.
6. Even if the phase difference E
is 180° in the above step, the
& and F beams may be
mistakenly on two different
beam pit tines as shown
below. F
Main
Be sure that the E and F beams are in the same pit line for
subsequent adjustments. 2
7. Remove the short between test pin TP1 and GND, and
TEST 1 and GND, and play back the fourth selection on
YEDS4.
8. Observe the waveform of the
signal between test pin E
and test pin F using the
dualtrace oscilloscope £
(Monitored in ALT mode).
The beam E and beam F are
in the same pit line if the
trigger of waveform F is
approximately 254s behind
the point (Position where
waveform holiows out}
where the waveform E is The twobeam are on the same pit line.
triggered. (100mV/DIV : 5«Sec/DiV)
When observation of the waveform is difficult, the trigger
level can be varied. When the beams are not in the same line,
return to step 1, and rotate the adjustment jig at the 180°
point. Confirm that the beams are in line at the 180° point.
Repeat steps 1 to 7 until confirmation of this is possible.
Note:
When the pick-up is replaced, it is adjusted as a unit, and
beams E and F can be brought in line and the phase made
180° by a slight adjustment. Slightly rotate the adjustment
jig when making adjustment. if the beams come out of line, it
is difficult to bring them back into the same pit fine.
ADJUSTMENT OF PICK-UP ANGLE
1. Mount the test disc YEDS4 on the turntable.
2. Turnon the power and play back the fourth selection.
3. Connect the oscilloscope between test pin HF and test pin
GND. Monitor the waveform of HF and rotate the angle
adjustment screw so that the waveform is at its maximum.
2
E-F BALANCE ADJUSTMENT
1. Turn on the power switch and mount test disc YEDS4 on the
table load. Set the unit to the STOP mode.
2. Short test pins TEST1 and GND of connector CN16.
3. Short test pin TP1 and test pin GND, and connect a DC
Voltmeter and oscilloscope to test pin TE of connector CN15
through the low-pass filter shown below.
Angle
Adjustment Screw
22K
TE ‘
| DC Voltmeter
! and
| Oscilloscope
GND
4, Press the F FWD button. The TRACK No. indication is “2”
and the disc begins to rotate. Continue to press the PLAY
button. The unit is rotating in this state with the tracking
servo turned off.
5. Adjust P101 so that the DC Voltmeter and oscilloscope is
OV+15mvV.
ADJUSTMENT PROCEDURES (continued)
ADJUSTMENT OF TURNTABLE HEIGHT
This adjustment must be made when the motor is replaced.
1. Attach the turntable so that
its top surface is 11.9mm _
from the top of the chassis. +
Spindle
Motor
2. Connect test pin FC of connector CN14 to a DC Voltmeter
and oscilloscope through the low-pass filter.
22K
FC
DC Voltmeter
and
Oscilloscope
GND
3. Turn on the power switch and playback the first selection on
test disc YEDS4.
4, Readjust the height of the turntable if the reading on the DC
Voltmeter is not in the range of OV+0.25V. (Increase the
height of the turntable when the OC Voltmeter reading is
positive, and decrease it when negative.)
ADJUSTMENT OF FOCUS/TRACKING GAIN
The measurement circuit shown below is necessary for
accurate adjustment of the focus and tracking gain. If this circuit
cannot be made, make adjustments using the simplified
procedure.
@ Remove connector CNS from
the pick-up and connect the
measurement circuit
between the PCB and = wmanece.
Pick-up. is
@ The iC used is TA7256P.
@ Volume — control 2k0-B
shorts IN and SG. 1kHz
1Vp-p is supplied from the
signal generator, and
adjustment is made for Pick-up
minimum output from OUT. CNS
-
Simplified adjustment Procedure
® Focus gain adjustment
P102 is set to a mechanical
center.
e@ Tracking gain adjustment
P103 is set to a mechanical
center.
Precise adjustment procedure
@ Focus gain adjustment
1. Connect the measurement
circuit shown above, turn on
the power switch, and mount
the test disc YEDS4.
2. Playback the first selection
on the test disc, and apply a
1,000Hz 0.5Vp-p signal from
the signal generator.
3. Observe the resurge waveforms on the oscilloscope, and
adjust P102 so that the phase difference of outputs X and Y
from the measurement circuit is 90°.
@ Tracking gain adjustment
1. Adjustment is made in the
same manner as for focus
gain. The input from the
frequency generator is set to
1,000Hz, 0.5Vp-p, and P103
is adjusted so that the phase
difference is 90°.
Dualtrace
Oscilloscope