Servo
Unit
Since the adjusting procedure differs from that described in “ADJUSTMENT PROCEDURES OF AUDIO PRODUCTS”, refer to
the Service Manual.
All the semivariable resistors must be set in the mechanical center position
r
Test Stage
_lAdjusling
Parts
Value/Adjusting Method
Instrument
Connecl~on
Set TEST MODE
0.
and
move
the
oickuo
to the center
__.-..--’
Set Test MODE
1
(make sure that the laser lamp
Ilghts)
-
__
Atier
loadmg
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.)
4
I-
Set TEST MODE 3 (Spin
servo
is turned on. and the disc rotates)
___-
.~-
Tracking
error
balance
adj
NVRI
T
Ii
‘1 (See Fig. 21-l)
I_.~___
Pin 6 (i/ZVcc) and
pin
4 (TGI)
of TP751
Set TEST MODE 4
(Tracklna
servo
IS
turned
on.)
.A/
Check
agaln
the HF signal waveform.
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. 22-l). (Any mode other than the test mode is acceptable.)
_I_
Focus offset
adj,
VR700
'4 (Fig. 22-Z)
Pin 6 (ll2Vcc) and
Din
1
(FGII
Tracking offset adj.
I
of TP751 ‘5
VR710
'6
Pin 6
(1/2Vcc)
and pin 4 (TGI)
nf
TP,K,
*‘7
Figure 22-1
I
“I
II
I-.
1
Adjust to obtain vertically symmetrical waveform (Fig. 21-I) with respect to reference DC level. The reference level is
l/ZVcc
[Amplitude of 0.5 to 1.5 Vpp)
” 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. 22-2) 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 CNP700.
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 minlmum (Fig. 22-2) 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. 22-3).
Figure 22-2
PICKUP
kD
SERVO
PWB-Bj
Figure 22-3
I
TP75 1
FOCUS TRACK IN
FOCUS
TRACK IN
OFFSET OFFSET
GAIN
GAIN
Figure 21-l
Figure 21-2
-2%
Figure 22-4 ADJUSTMENT POINTS
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