JVC HR-S5000U Service Manual page 49

DEMODU LATOR CIRCUIT
2 . 8
Note: 1 . U n less otherwise specified, all test points and adjustments are located o n the D EM O DU LATOR board .
2. Un less otherwise specified, set an audio multiplex
I F signal : 82 d Bµ/75 Q load, co lor bar 87 .5% (TIOdulation .
No. Item Check Point
Equipmen · t required:
1 . Oscil loscope
2. If sweep signal generator with suitable markers (P I F , S I F, etc. )
3. Sweeper probe (sweep signal supply) as shown below.
1 Stero m id point
vco
of R76
and R23
2 Stereo I C 1 -37 pin
filter
3 SAP fi lter
I C 1 -6 pin
4
dBX level l'C1":24
mutch
&
[ ( L- R )
SAP]
5 OUTPUT CN 1 -4 pin
L E V E L
CN 1 -7 pin
&
[ ( L + R )
SAP]
TV
signal generator as fo l lows;
&
Adjustment
Signal Mode
Parts
R23 • No signal
(ST VCO • E-E mode
ADJ)
R 3 • Tuner mode
(ST
F I LT E R ADJ)
R5 • Tuner mode
(SAP
F I LTE R ADJ )
R26
• Tuner mode
( L-R
LEV E L )
R 1 8
(SAP
LEVEL)
R22 • Tuner mode
( L + R
LEV E L)
R55
(SAP
LEVE L)
Description
:
C
1 000P
, - - - t- t
Shi • l d
_/L
Sweeper probe
R. 75
Fig. 2-8-1
1 . Connect a frequency counter to m id point of R76
and R23. (use low i nd uctance (under 1 0P F ) and
high i mpedance (over 1 MQ) probe . )
2 . Adjust R23 for 62.936 k H z ± 1 00 H z .
1 . Supply a n audio sinewave signa l (78.67 k Hz,
0 d B m ) to CN2, 1 pin.
2 . Connect a level meter to I C 1 , 37 pin a nd adjust R3
for minimum level ( less than -40 d B m ) .
1 . Supply a n audio si newave signal (62.94 k Hz,
0 d Bm ) to CN2, 1 pin .
2. Co nnect a level meter to IC1 , 6 pin a nd adjust R5
for minimum level ( less than -35 d B m ) .
1 , . .Use a sweep probe a s shown i n F i g . 2-8-1 and
apply I F signal to SAW 1 .
2 . Set a signa l generator mode to stereo ( L- R ) 300 Hz
8
1 4% and connect a level meter to I C1 , 24 pin and
G N D ( terminal of C9 ) .
3. Adjust R 2 6 for 60 ± 3 mVrms.
4 . Set a signal generator mode to SAP 300 H z 1 4%
8
a nd connect a level meter to I C 1 , 24 pin and G N D
( termina l o f C9) .
5. Adj ust R 1 8 for 60 ± 3 mVrms .
1 . Set a signal generator mode to stereo ( L + R )
1 k H z 1 00%, connect a level meter t o CN 1 , 4 pin.
Adjust R22 for -17 ± 0 .5 d Bm .
2 . Set a sig na l generator mode t o SAP 1 k H z 1 00%,
connect a level meter to C N 1 , 7 pin . Adjust R55
for -1 7 ± 0 .5 d Bm .
S h orter than 8
cm
S h orter t h an
0
cm
5
2-1 1