Electrical Block Checking - Sony CDP-XB920 Service Manual

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
SERVO board
TP(FE)
TP(VC)
Procedure :
1. Connect oscilloscope to test point TP (FE) on SERVO board.
2. Connect between test point TP (FEI) and TP (VC) by lead wire.
Turn U (power) switch on.
3.
Put disc (YEDS-18) in and turn U (power) switch on again
4.
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
between 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
brightness to obtain best waveform.
RF Level Check
SERVO board
TP(RF)
TP(VC)
Procedure :
1. Connect oscilloscope to test point TP (RF) on SERVO board.
Turn U (power) switch on.
2.
3. Put disc (YEDS-18) in to play the number five track.
4. Confirm that oscilloscope waveform is clear and check RF
signal level is correct or not.
SECTION 5

ELECTRICAL BLOCK CHECKING

oscilloscope
symmetry
A
within 3 ± 1Vp-p
B
oscilloscope
— 11 —
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 (1 Track Jump) Check
(Without remote commander)
SERVO board
TP(TE)
TP(VC)
Procedure :
1. Connect oscilloscope to test point TP (TE) on SERVO board.
Turn U (power) switch on.
2.
3. Put disc (YEDS-18) in to play the number five track.
4. Press the "P (Pause)" button. (Becomes the 1 track jump mode)
5. Check the level B of the oscilloscope's waveform and the A
(DC voltage) of the center of the Traverse waveform.
Confirm the following :
A/B x 100 = less than ± 22%
1track jump waveform
0V
level : 1.3 ± 0.6 Vp-p
E-F Balance (Traverse) Check
(With remote commander)
SERVO board
TP(TE)
TP(VC)
Procedure :
1. Connect oscilloscope to test point TP (TE) on SERVO board.
2. Connect the test point TP21 (ADJ) on MAIN board to the
ground with a lead wire.
Turn the U (power) switch on to set the ADJ mode.
3.
4. Put disc (YEDS-18) in to play the number five track.
5. Press the "4" button. (The tracking servo and the sledding servo
are turned OFF.)
VOLT/DIV : 200mV
TIME/DIV : 500ns
level : 1.45 ± 0.25 Vp-p
oscilloscope
Center of the waveform
B
A (DC voltage)
symmetry
oscilloscope