Servo Unit
Since the adjusting procedure differs from that described in “ADJUSTMENT PROCEDURES OF
AUDIO
PRODUCTS[IT]“, refer to the
Service Manual.
All the semivariable resistors must be set in the mechanical center position.
1
TP75i
*7
’
j
1 Adjust to obtain vertically symmetrical waveform (Fig.
I
l-l) with respect to reference DC level. The reference level is
1/2Vcc.
(Amplitude of 0.5 to 1.5 Vpp)
/
Test
Stage Adjusting
Park
Value/Adjusting
Method
/
instrument
Connection
Set TEST MODE
0,
and move the pickup to the center
Set Test MODE 1 (make sure that the laser lamp lights)
Alter loading a disc, set to TEST MODE 2. (Check to see that focus servo is ON.: The disc does not rotate,
and
a whining sound is heard.)
Set TEST MODE 3 (Spin servo is turned on, and the disc rotates)
Tracking error balance adj. NVRl
*l
(See Fig. 1 l-i)
Pin 6 (1BVcc) and pin 4
(TGl)
of
TP751
Set TEST MODE 4 (Tracking servo is turned on.)
Check the HF signal waveform
-
Focus gain adj.
WI751
Tracking gain adj.
VR750
Check again the HF signal waveform.
Amplitude of 1.5-2.0
Vp-p
(See
Fig. 1 l-2.)
Adjust to obtain the same
waveform on CHI and CH2.
*2
Adjust to obtain the same
waveform on CHI and
CH2.
l
3
Pin 3 (HF) and pin 7 (GND) of
TP751
Pin 1
(FGl)
and pin 5 (FG2) of
TP751 and ground (The relay
circuit is used.)
Pin 4
(TGl)
and pin 2 (TG2) of
TP751
and ground (The relay
circuit is used.)
Set TEST MODE 5, and make sure that track No. and time are displayed.
Stick black tape on the disc, and play that section (Fig.
12-1).
(Any mode other than the test mode is acceptable.)
Focus offset adj.
VR700
*4 (Fig. 12-2)
Pin 6
(1/2Vcc)
and pin 1
(FGl)
of
TP751
*5
Tracking offset adj. VR710
*6
Pin 6
(1/2Vcc)
and
Pin
4
(TGl)
of
*
2 Input oscillation frequency: 1.3
kHz,
100
mV
rms
*
3 Input oscillation frequency: 1.5
kHz,
300
mV
rms
*
4 Watch the monitor. Adjust so that the error waveform is uniform and minimum (Fig. 12-2) and the audio output is played properly
without noise (track jump noise) and free from skips and pauses.
*
5 The appropriate measuring range of the oscilloscope is
50mV
and
0.5mS.
Connect the trigger to pin 14 (HFOK) of CNS700.
Trigger the coupling at DC and
(-)
slope. Observe the waveform in the normal trigger mode.
*
6 Watch the monitor. Adjust so that the error waveform is uniform and minimum (Fig. 12-2) and the audio output is played properly
without noise (track jump noise).
*
7 The appropriate measuring range of the oscilloscope is
O.lV
and
0.5mS.
The trigger is the same as *5.
(Reference) When the noise element of the error waveform is large and unclear, observe the waveform through the low-pass filter
(Fig. 12-3).
Reference
DC Level
-
l/2
vcc
1. 5
-
2.0
VP -
P
OSCILLOSCOPE
TP751
Pin 3
UNIT
IQ
w
Figure
11-2
Figure
11-l
-
13
-
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