Sony LBT-A57CD Service Manual page 29

43/M54
'SECTION 3
ELECTRICAL BLOCK CHECKING
Note:
1. CD Block basically constructed to operate with-out
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 10M2 im-pedance.
4. Clean an object lens by an applicator with neutral
detergent when the signal level is low than specified
value with the following checks.
S Curve Check
oscilloscope
BD board
—
TP (FE) ow—o}
TP (VC) ow—lo-
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 and actuate the focus serch.
(actuate the focus serch when disc table is moving in
and out.)
4. Check the oscilloscope waveform (S curve) is
symmetrical between A and B. And confirm peak to
peak level within 31Vp-p.
S curve waveform
5. After check, remove the lead wire connected in step 2.
Note: + Try to mesure several times to make sure that
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
oscilloscope
BD board
Capa 3
TP (RFO)O@—j0F
TP. (VC) O——10-
Procedure :
1. Connect oscilloscope to test point TP (RFO) on BD
board.
2. Turn Power switch on.
3. Put disc (YEDS-18) in and playback.
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 wave-
form.
VOLT/DIV : 200mV
TIME/DIV : 5000S
RF signal waveform
KK
WR
AWB
DOAK
NY
level :
+0.2
1.2793 Vee
E-F Balance Check
oscilloscope
BD board
os
TP (TE)
ow—o>
TP (VC) ow—lo-
Procedure:
1. Connect test point TP (ADJ) to ground and TP (TEI)
to TP (VC) with lead wire.
2, Connect oscilloscope to test point TP (TE) on BD
board.
3. Turn Power switch on.
. Put disc (YEDS-18) in and playback.
5. Confirm that the osilloscope waveform is sym-metrical
on the top and bottom in relation to OV, and check
this level.
rs
Traverse oscilloscope
mn N' na
ial
mil V vie
symmetry
level: 2:1Vp-p
6. Remove the lead wire connected in step 1.