Sony MHC-6800 Service Manual page 88

SECTION 3
ELECTRICAL ADJUSTMENTS
Note:
1. CD Block basically constructed to operate without adjus-
tment. Therefore, check each item in order given.
2, Use YEDS-18 disc (3-702-101-01) unless otherwise indicat-
ed.
3. Use the oscilloscope with more than 10MQ impedance.
4. Clean an object lens by an applicator with neutral deter-
gent when the signal level is low than specified value
with the following checks.
S Curve Check
oscilloscope
BD board
TPCFEO) ow /OF
TP(VC) O—w—0-
Procedure :
1. Connect oscilloscope to test point TP (FEO) on BD
board.
2. Connect between test point TP (FES) 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 symmetri-
cal between A and B. And confirm peak to peak level
within 341Vp-p.
S curve waveform symmetry
within 3 +1Vp-p
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 OC)
TP(RFO) Ot 0+
TP(VC) Om—*—7°
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 waveform.
VOLT/DIV: 200mV RF signal waveform
TIME/DIV: 500nS
Wy
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OXXXXAMAMAKAY.
| 1:2 2888 Vee
AION
E-F Balance Check
oscilloscope
BD board C)
—s
TP(TEO) om °F
TP(VC) Q—e—t0-
Procedure :
1, Connect test point TP (ADJ) to ground and TP (TES) to
TP (VC) with lead wire.
2. Connect oscilloscope to test point TP (TEO) on BD
board.
3. Turn Power switch on.
4, Put disc (YEDS-18) in and playback.
Confirm that the osilloscope waveform is symmetrical on
the top and bottom in relation to 0V, and check this level.
Traverse oscilloscope
6. Remove the lead wire connected in step 1.
level: 2£1Vpp