Read Sony XR-4790 / XR-4800 / XR-7850 (serv.man2) Service Manual online
– 14 –
TUNER SECTION
0 dB=1 µV
Cautions during repair
When the tuner unit is defective, replace it by a new one be-
cause its internal block is difficult to repair.
cause its internal block is difficult to repair.
Note:
Adjust the tuner section in the sequence shown below.
1. FM Auto Scan/Stop Level Adjustment.
2. FM Noise Focus Adjustment.
3. FM Stereo Separation Adjustment.
4. AM (MW) Auto Scan/Stop Level Adjustment.
2. FM Noise Focus Adjustment.
3. FM Stereo Separation Adjustment.
4. AM (MW) Auto Scan/Stop Level Adjustment.
FM Auto Scan/Stop Level Adjustment
Setting:
[SOURCE]
button: FM
Procedure:
1. Set to the test mode. (See page 13).
2. Push the
1. Set to the test mode. (See page 13).
2. Push the
[SOURCE]
button and set to FM.
Display
3. Adjust with the volume RV2 on TU1 so that the “FM” indica-
tion turns to “FMI” indication on the display window.
But, in case of already indicated “FMI”, turn the RV2 so that
put out light “I” indication and adjustment.
But, in case of already indicated “FMI”, turn the RV2 so that
put out light “I” indication and adjustment.
Display
Adjustment Location: See page 16.
FM RF signal
generator
Carrier frequency : 98.0 MHz
Output level
Output level
: 22 dB (12.6
µ
V)
Mode
: mono
Modulation
: 1 kHz, 22.5 kHz deviation (30%)
0.01
µ
F
set
antenna jack (J1)
FM
98.0
SHUF1
FM
98.0
SHUF1
FM Noise Focus Adjustment
Setting:
[SOURCE]
button: FM
Procedure:
1. Tune the 98.00 MHz.
2. The then output level is supposing that (A) dB.
3. Adjust with the volume RV3 on TU1 so that the output level is
1. Tune the 98.00 MHz.
2. The then output level is supposing that (A) dB.
3. Adjust with the volume RV3 on TU1 so that the output level is
(A) –32 ±2 dB then signal generator input set to –20 dB.
Adjustment Location: See page 16.
FM Stereo Separation Adjustment
Setting:
[SOURCE]
button: FM
Procedure:
FM RF signal
generator
Carrier frequency : 98.00 MHz
Output level
Output level
: 60 dB (1 mV)
Mode
: mono
Modulation
: 1 kHz, 75 kHz deviation (100%)
0.01
µ
F
set
antenna jack (J1)
+
–
–
LINE OUT
level meter
10
Ω
FM Stereo
Level meter
Level meter
signal generator
connection
reading (dB)
output channel
L-CH
L-CH
A
B
R-CH
L-CH
Adjust RV4 on TU1
for minimum reading.
R-CH
R-CH
C
D
L-CH
R-CH
Adjust RV4 on TU1
for minimum reading.
FM RF signal
generator
Carrier frequency : 98.0 MHz
Output level
Output level
: 70 dB (3.2 mV)
Mode
: stereo
Modulation
: main: 1 kHz, 33.75 kHz deviation (45%)
sub: 1 kHz, 33.75 kHz deviation (45%)
19 kHz pilot: 7.5 kHz deviation (10%)
19 kHz pilot: 7.5 kHz deviation (10%)
0.01
µ
F
set
antenna jack (J1)
+
–
–
LINE OUT
level meter
10
Ω
L-CH Stereo separation: A-B
R-CH Stereo separation: C-D
The separations of both channels should be equal.
R-CH Stereo separation: C-D
The separations of both channels should be equal.
Specification: Separation more than 28dB
Adjustment Location: See page 16.
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