Sony HCD-V818 Service Manual page 19

CD SECTION
NOTE :
1. CD Block is basically designed 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 an oscilloscope with more than 10MΩ impedance.
4. Clean the object lens by an applicator with neutral detergent when
the signal level is low than specified value with the following
checks.
S Curve Check
BD board
TP (FE)
TP (VC)
Procedure :
1. Connect oscilloscope to test point TP (FE) on BD board.
2. Connect between test point TP (FEI) and TP (VC) 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.)
5. Check the oscilloscope waveform (S-curve) is symmetrical be-
tween A and B.
And confirm peak to peak level within 3±1 Vp-p.
S-curve waveform
6. After check, remove the lead wire connected in step 2.
Note : • Try to measure several times to make sure than the ratio
of A : B or B : A is more than 10 : 7.
• Take sweep time as long as possible and light up the bright-
ness to obtain best waveform.
RF Level Check
BD board
TP (RF)
TP (VC)
Procedure :
1. Connect oscilloscope to test point TP (RF) on BD board.
2. Turned Power switch on.
3. Put disc (YEDS-18) in to play the number five track.
4. Confirm that oscilloscope waveform is clear and check RF sig-
nal level is correct or not.
oscilloscope
+
–
symmetry
A
Within 3 ± 1 Vp-p
B
oscilloscope
+
–
Note : A clear RF signal waveform means that the shape "◊" can
be clearly distinguished at the center of the waveform.
RF signal waveform
E-F Balance (Traverse) Check (Without remote comander)
BD board
TP (TE)
TP (VC)
Procedure :
1. Short-circuit SL502 of the video board to GND.
2. Connect oscilloscpe to test point TP (TE) on BD board.
3. Turned Power switch on. Press FUNCTION button to select
CD.
4. Set a disc (YEDS-18) and play.
5. Press the PLAY MODE button.
(The sledding servo is turned OFF.)
6. Check the level B of the oscilliscope's waveform and the A (DC
voltage) of the center of the Traverse waveform.
Confirm the following :
A/B x 100 = less than ± 7%
Traverse waveform
0V
7. Press the PLAY MODE button. (The tracking servo and sledding
servo are turned ON.) Confirm the C (DC voltage) is almost
equal to the A (DC voltage) is step 6.
Traverse waveform
0V
– 19 –
VOLT/DIV : 200mV
TIME/DIV : 500ns
+0.25
level : 1.3 Vp-p
–0.20
oscilloscope
+
–
Center of the waveform
B
A (DC voltage)
level : 500 mV ± 100 mVp-p
Sled servo Sled servo
OFF
ON
C (DC
voltage)