Sony HCD-VX8 Service Manual page 16

CD SECTION
Note:
1. CD Block is 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 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)
Adjustment Location: BD board
Procedure :
1. Connect the oscilloscope to test points TP (FE) and TP (VC).
2. Connect TP (FEI) and GND, and TP (AGCCON) and GND of
the BD board with lead wires.
3. Press the 1/u button to turn the set ON.
4. With the disc (YEDS-18) loaded, press the ^ button and
perform focus search. (Focus search will be performed in the
same way even while the disc table is pushed in and out.)
5. Check the symmetry and peak to peak level of the oscilloscope
waveform (S curve) at this time.
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.
Adjustment Location: BD board
RF Level Check
BD board
TP (RF)
TP (VC)
Procedure :
1. Connect oscilloscope to test point TP (RF) and TP (VC) on BD
board.
2. Connect TP (AGCCON) and GND of the BD board with lead
wires.
3. Press the 1/u button to turn the set ON.
4. Put disc (YEDS-18) in and playback 5track.
5. Confirm that oscilloscope waveform is clear and check RF sig-
nal level is correct or not.
6. After check, remove the lead wire connected in step 2.
oscilloscope
+
–
symmetry
A
Within 4.0 ± 1.0 Vp-p
B
oscilloscope
+
–
– 16 –
Note: 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
BD board
TP (TE)
TP (VC)
Adjustment Location: BD board
Procedure :
1. Connect oscilloscpe to test point TP (TE) on BD board.
2. Short-circuit SL502 of the video board to GND.
3. Turned Power switch on. Press FUNCTION button to select
CD.
4. Put disc (YEDS-18) in to play the number five track.
5. Press the PLAY MODE/DOLBY NR button. (The tracking
servo and the sledding servo are 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 ± 22%
Traverse waveform
0V
7. Press the PLAY MODE/DOLBY NR 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 7.
Traverse waveform
0V
Tracking servo
Sled servo
OFF
8. Desolder the short-land (SL502) short-circuited at step 2.
Adjustment Location: BD board
VOLT/DIV : 200mV
TIME/DIV : 500ns
level : 1.75 ± 0.25 Vp-p
oscilloscope
+
–
Center of the waveform
B
A (DC voltage)
level : 1.3 ± 0.6 Vp-p
C (DC
voltage)
Tracking servo
Sled servo
ON