Read Sony MHC-VX3 (serv.man2) Service Manual online
16
CD SECTION
Note:
1.
CD Block is basically constructed to operate without
adjustment. Therefore, check each item in order given.
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 10M
Ω
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.
when the signal level is low than specified value with the
following checks.
S Curve Check
Adjustment Location: BD board
Procedure :
1.
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.
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.)
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.
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
brightness to obtain best waveform.
Adjustment Location: BD board
RF Level Check
Procedure :
1.
1.
Connect oscilloscope to test point TP (RF) and TP (VC) on BD
board.
board.
2.
Connect TP (AGCCON) and GND of the BD board with lead
wires.
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
signal level is correct or not.
signal level is correct or not.
6.
After check, remove the lead wire connected in step 2.
oscilloscope
BD board
TP (FE)
TP (VC)
TP (VC)
+
–
–
oscilloscope
BD board
TP (RF)
TP (VC)
TP (VC)
+
–
–
E-F Balance (Traverse) Check
oscilloscope
BD board
TP (TE)
TP (VC)
TP (VC)
+
–
–
Adjustment Location: BD board
Procedure :
1.
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.
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.)
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%
(DC voltage) of the center of the Traverse waveform.
Confirm the following :
A/B x 100 = less than ± 22%
Traverse waveform
0V
level : 1.3
±
0.6 Vp-p
A (DC voltage)
Center of the waveform
B
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.
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
C (DC
voltage)
voltage)
Tracking servo
Sled servo
OFF
Sled servo
OFF
Tracking servo
Sled servo
ON
Sled servo
ON
symmetry
A
B
Within 4.0
±
1.0 Vp-p
Note:
Clear RF signal waveform means that the shape “
◊
” can be
clearly distinguished at the center of the waveform.
RF signal waveform
VOLT/DIV : 200mV
TIME/DIV : 500ns
TIME/DIV : 500ns
level : 1.75
±
0.25 Vp-p
8.
Desolder the short-land (SL502) short-circuited at step 2.
Adjustment Location: BD board
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