Sony HCD-H331 Service Manual page 12

CD SECTION
Note :
1. CD Block basically constructed to operate without adjustment.
Therefore, check each item in order given.
2. Use YEDS-18 disc (3-702-101-01) unless otherwise indicated.
3. Use the oscilloscope with more than 10MΩ impedance.
4. Clean an object lens by an applicator with neutral detergent when
the signal level is low than specified value with the following
checks.
Focus Bias Adjustment
This adjustment is to be done when the optical block is replaced.
Adjustment procedure :
oscilloscope
(DC range)
BD board
TP (RF)
TP (VC)
1. Connect oscilloscope to test point TP (VC) and TP (RF) on BD
board.
2. Turned power switch ON. (Stop mode)
3. Put disc (YEDS-18) in and press the fl button.
4. Adjust RV101 so that the oscilloscope waveform is as shown in
the figure below (eye pattern).
A good eye pattern means that the diamond shape (◊) in the center
of the waveform can be clearly distinguished.
RF signal reference waveform (eye pattern)
r
When observing the eye pattern, set the oscilloscope for AC range
and raise vertical sensitivity.
Adjustment Location : MAIN board. (see page 13)
S-Curve Check
BD board
TP (FEO)
TP (VC)
Procedure :
1. Connect oscilloscope to test point TP (VC) and TP (FEO) on BD
board.
2. Connect between test point TP (FOK) and GND by lead wire.
3. Turned Power switch on.
4. Put disc (YEDS-18) in and turned Power switch on again and
actuate the focus search. (actuate the focus search when disc table
is moving in and out.)
+
–
VOLT/DIV : 0.2V
TIME/DIV : 500ns
1.3 ± 0.3Vp-p
oscilloscope
+
–
5. Check the oscilloscope waveform (S-curve) is symmetrical
between A and B. And confirm peak to peak level within
2.4 ± 0.7Vp-p.
S-curve waveform
6. After check, remove the lead wire connected in step 2.
Note :
Try to measure several times to make sure that the ratio of
r
A : B or B : A is more than 10 : 7.
Take sweep time as long as possible and light up the bright-
r
ness to obtain best waveform.
Adjustment Location : BD board. (see page 13)
RF Level Check
BD board
TP (RF)
TP (VC)
Procedure :
1. Connect oscilloscope to test point TP (VC) and TP (RF) on BD
board.
2. Turned Power switch on.
3. Put disc (YEDS-18) in and press the fl button.
4. Confirm that oscilloscope waveform is clear and check RF signal
level is correct or not.
Note :
Clear RF signal waveform means that the shape "◊" can be clearly
distinguished at the center of the waveform.
RF signal waveform
r
Adjustment Location : BD board. (see page 13)
– 12 –
symmetry
A
within 2.4 ± 0.7Vp-p
B
oscilloscope
+
–
VOLT/DIV : 200mV
TIME/DIV : 500ns
level : 1.3 ± 0.3Vp-p