Sony HCD-GN700 / HCD-GX8800 / MHC-GN700 / MHC-GX8800 Service Manual ▷ View online
21
HCD-GN700/GX8800
2. Turn the adjustment screw and check output peaks. If the peaks
do not match for L-CH and R-CH, turn the adjustment screw
so that outputs match within 1dB of peak.
so that outputs match within 1dB of peak.
3. Mode: Playback
4. After the adjustments, apply suitable locking compound to the
pats adjusted.
Adjustment Location: Playback Head (Deck A).
Record/Playback/Erase Head (Deck B).
REC BIAS ADJUSTMENT DECK B
Procedure:
In the MC test mode, the “REC memory mode” is convenient for
this adjustment. In the “REC memory mode” , when the REC starts
the input signal FUNCTION is switched to VIDEO automatically.
When the REC stops, the tape returns near to the recording start
position.
In the MC test mode, the “REC memory mode” is convenient for
this adjustment. In the “REC memory mode” , when the REC starts
the input signal FUNCTION is switched to VIDEO automatically.
When the REC stops, the tape returns near to the recording start
position.
1. Press
MD (VIDEO)
button to select VIDEO. (This step is not
necessary if the above test mode has already been set)
2. Insert a tape into deck B.
3. After press
3. After press
[REC PAUSE/START]
button, press
[REC PAUSE/
START]
button, then recording start.
4. Mode: Record
5. Mode: Playback
6. Confirm the playback signal recorded in step 3 becomes
adjustable level as follows.
If these levels are not adjustable level, adjust the RV304 (L-
CH) and RV354 (R-CH) on the MAIN board to repeat steps 4
and 5.
If these levels are not adjustable level, adjust the RV304 (L-
CH) and RV354 (R-CH) on the MAIN board to repeat steps 4
and 5.
Adjustable level: Playback output of 315 Hz to playback output
of 10 kHz:
±
1.0 dB
Adjustment Location: MAIN board
Screw
position
position
L-CH
peak
peak
within
1dB
1dB
Output
level
level
L-CH
peak
peak
R-CH
peak
peak
within
1dB
1dB
Screw
position
position
R-CH
peak
peak
MAIN
board
CN301
set
board
CN301
set
test tape
P-4-A100
(10 kHz, –10 dB)
P-4-A100
(10 kHz, –10 dB)
pin
3
oscilloscope
L-CH
R-CH
V
H
waveform of oscilloscope
in phase 45
°
90
°
135
°
180
°
good
wrong
pin
2
pin
1
L
R
attenuator
set
MAIN board
MD/VIDEO (AUDIO) IN (J750)
MD/VIDEO (AUDIO) IN (J750)
1) 315 Hz
2) 10 kHz
2) 10 kHz
50 mV (–23.8 dB)
600
Ω
blank tape
CN-123
CN-123
AF OSC
+
–
–
set
recorded
portion
portion
MAIN board
CN301 Pin
CN301 Pin
2
(GND)
MAIN board
CN301
Pin
CN301
Pin
1
(L-CH)
Pin
3
(R-CH)
level meter
forward
reverse
22
HCD-GN700/GX8800
CD SECTION
Note:
1. CD Block is basically designed to operate without adjustment. There-
fore, 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
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.
S-curve Check
Connection:
Procedure:
1.
1.
Connect an oscilloscope to test point TP4 (FE) and TP 7(DVC)
on the CD board.
on the CD board.
2.
Turn the power on.
3.
Put the disc (YEDS-18) in and turned power switch on again
and actuate the focus search. (actuate the focus search when
disc table is moving in and out)
and actuate the focus search. (actuate the focus search 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 2.4
between A and B. And confirm peak to peak level within 2.4
±
1 Vp-p.
S-curve waveform
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.
Checking Location: CD board (SIDE B)
(See page 24.)
– MAIN BOARD (Component Side) –
REC LEVEL
ADJUSTMENT
REC BIAS ADJUSTMENT
CN301
IC301
3
1
(R-CH)
(R-CH)
(L-CH)
(L-CH)
RV301
RV351
RV304
RV354
+
–
–
CD board
TP4 (FE)
TP7 (DVC)
oscilloscope
A
B
symmetry
within 2.4
±
1 Vp-p
REC LEVEL ADJUSTMENT DECK B
Procedure:
In the MC test mode, the “REC memory mode” is convenient for
this adjustment. In the “REC memory mode” , when the REC starts
the input signal FUNCTION is switched to VIDEO automatically.
When the REC stops, the tape returns near to the recording start
position.
In the MC test mode, the “REC memory mode” is convenient for
this adjustment. In the “REC memory mode” , when the REC starts
the input signal FUNCTION is switched to VIDEO automatically.
When the REC stops, the tape returns near to the recording start
position.
1. Press
MD (VIDEO)
button to select VIDEO. (This step is not
necessary if the above test mode has already been set)
2. Insert a tape into deck B.
3. After press
3. After press
[REC PAUSE/START]
button, press
[REC PAUSE/
START]
button, then recording start.
4. Mode: Record
5. Mode: Playback
6. Confirm the play back signal recorded in step 3 becomes
adjustable level as follows.
If these levels are not adjustable level, adjust the RV301 (L-
CH) and RV351 (R-CH) on the MAIN board to repeat steps 4
and 5.
If these levels are not adjustable level, adjust the RV301 (L-
CH) and RV351 (R-CH) on the MAIN board to repeat steps 4
and 5.
Adjustable level:
CN301 PB level: 47.2 to 53.0 mV (–24.3 to –23.3 dB)
Adjustment Location: MAIN board
CN301 PB level: 47.2 to 53.0 mV (–24.3 to –23.3 dB)
Adjustment Location: MAIN board
set
MAIN board
MD/VIDEO (AUDIO) IN (J117)
315 Hz, 50 mV (–23.8 dB)
MD/VIDEO (AUDIO) IN (J117)
315 Hz, 50 mV (–23.8 dB)
blank tape
CS-123
CS-123
600
Ω
attenuator
AF OSC
+
–
–
set
recorded
portion
portion
MAIN board
CN301 Pin
CN301 Pin
2
(GND)
MAIN board
CN301
Pin
CN301
Pin
1
(L-CH)
Pin
3
(R-CH)
level meter
23
HCD-GN700/GX8800
RFAC Level Check
Connection:
Procedure:
1.
1.
Connect an oscilloscope to test point TP5 (RFAC) and TP
7(DVC) on the CD board.
7(DVC) on the CD board.
2.
Turn the power on.
3.
Put the disc (YEDS-18) in to playback the number five track.
4.
Confirm that oscilloscope waveform is clear and check RFAC
signal level is correct or not.
signal level is correct or not.
Note:
A clear RFAC signal waveform means that the shape “
◊
” can be
clearly distinguished at the center of the waveform.
RFAC signal waveform
Checking Location: CD board (SIDE B)
(See page 24.)
E-F Balance Check
Connection:
Procedure:
1.
1.
Connect an oscilloscpe to test point TP2 (TE) and TP7 (DVC)
on the CD board.
on the CD board.
2.
Turn the power on.
3.
Select the function “CD”.
4.
Press three buttons of
[ENTER]
,
M
, and
[SURRUUND MODE]
simultaneously to set the CD service
mode.
5.
Put the disc (YEDS-18) in to playback the number five track.
6.
Press the
.
button. The message “TRAVERSE” is
displayed. (The tracking servo and the sledding servo are turned
OFF)
OFF)
7.
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
(DC voltage) of the center of the Traverse waveform.
Confirm the following :
A/B x 100 = less than
±
22%
Traverse Waveform
8.
Press the
.
button. The message “TRAVERSE” is
displayed. (The tracking servo and sledding servo are turned
ON)
Confirm the C (DC voltage) is almost equal to the A (DC
voltage) is step 5.
ON)
Confirm the C (DC voltage) is almost equal to the A (DC
voltage) is step 5.
9. To exit from this mode, perform as follows.
1) Move the optical pick-up to the most inside track.
2) Press three buttons of
2) Press three buttons of
x
,
[CLEAR]
, and
[DISPLAY]
simultaneously. (cold reset)
Notes:
• Always move the optical pick-up to most inside track when
exiting from this mode. Otherwise, a disc will not be unloaded.
• Do not run the sled motor excessively, otherwise the gear can
be chipped.
Traverse Waveform
Checking Location: CD board (SIDE B) (See page 24.)
+
–
–
CD board
TP5 (RFAC)
TP7 (DVC)
oscilloscope
VOLT/DIV: 200 mV
TIME/DIV: 500 ns
TIME/DIV: 500 ns
level: 0.9
±
0.4 Vp-p
+
–
–
CD board
TP2 (TE)
TP7 (DVC)
oscilloscope
0V
B
level: 1.0
±
0.5 Vp-p
Center of
the waveform
the waveform
A (DC
voltage)
0V
Tracking servo
Sled servo
ON
C (DC
voltage)
voltage)
Tracking servo
Sled servo
OFF
24
HCD-GN700/GX8800
Checking Location:
– CD BOARD (SIDE B) –
TP4 (FE)
TP2 (TE)
TP5 (RFAC)
TP7 (DVC)
IC104
IC101
IC103
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