Tuner Section - Sony XR-4800 Service Manual

(4800: E model only)

TUNER SECTION

XR-4790 and XR-4800 US/Canadian model, a tuner section is no
adjustment.
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
FREQUENCY SELECT switch: 10 k
FM RF signal
generator
0.01 µ F
Carrier frequency : 97.9 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 15).
[SOURCE]
2. Push the button and set to FM.
Display
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.
Display
SHUF1
Adjustment Location: See page 18.
antenna jack (J1)
set
97. 9
97. 9
FM Noise Focus Adjustment
Setting:
[SOURCE]
button: FM
FREQUENCY SELECT switch: 10 k
FM RF signal
antenna jack (J1)
generator
0.01 µ F
Carrier frequency : 97.9 MHz
Output level : 60 dB (1 mV)
Mode : mono
Modulation : 1 kHz, 75 kHz deviation (100%)
Procedure:
1. Tune the 97.9 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 18.
FM Stereo Separation Adjustment
Setting:
[SOURCE]
button: FM
FREQUENCY SELECT switch: 10 k
FM RF signal
antenna jack (J1)
generator
0.01 µ F
Carrier frequency : 97.9 MHz
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%)
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 18.
– 16 –
level meter
10 k Ω
set
LINE OUT
level meter
10 k Ω
set
LINE OUT
Level meter Level meter
connection reading (dB)
A
L-CH
B
L-CH Adjust RV4 on TU1
for minimum reading.
C
R-CH
D
R-CH Adjust RV4 on TU1
for minimum reading.
+
–
+
–