Tuner Section - Sony XR-3750 Service Manual

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.
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
FM Auto Scan/Stop Level Adjustment
Setting:
[SOURCE]
button: FM
FM RF signal
generator
0.01 µ F
Carrier frequency : 98.0 MHz
: 22 dB (12.6 µ V)
Output level
Mode : mono
Modulation : 1 kHz, 22.5 kHz deviation (30%)
Procedure:
1. Set to the test mode. (See page 13)
[SOURCE]
2. Push the button and set to FM.
FM
SHUF1
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.
SHUF1
Adjustment Location: See page 16.
antenna jack (J1)
set
Display
98. 0
Display
98. 0
FM Noise Focus Adjustment
Setting:
[SOURCE]
button: FM
FM RF signal
generator
0.01 µ F
Carrier frequency : 98.0 MHz
Output level : 60 dB (1 mV)
Mode : mono
Modulation : 1 kHz, 75 kHz deviation (100%)
Procedure:
1. Tune the 98.0 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
FM RF signal
generator
0.01 µ F
Carrier frequency : 98.0 MHz
Output level : 60 dB (1 mV)
Mode : mono
Modulation : 1 kHz, 75 kHz deviation (100%)
Procedure:
FM Stereo
signal generator
output channel
L-CH
R-CH
R-CH
L-CH
L-CH Stereo separation: A-B
R-CH Stereo separation: C-D
The separations of both channels should be equal.
Specification: Separation more than 30 dB
Adjustment Location: See page 16.
– 14 –
antenna jack (J1)
10 k Ω
set
LINE OUT
antenna jack (J1)
10 k Ω
set
LINE OUT
Level meter Level meter
connection reading (dB)
L-CH
L-CH Adjust RV4 on TU1
for minimum reading.
R-CH
R-CH Adjust RV4 on TU1
for minimum reading.
level meter
+
–
level meter
+
–
A
B
C
D