Read Sony XR-1790 (serv.man3) Service Manual online
– 2 –
2.
ELECTRICAL ADJUSTMENTS
• AM section adjustment is done automatically in this set.
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 Stereo Separation Adjustment
2. FM Stereo Separation Adjustment
FM Auto Scan/Stop Level Adjustment
Setting:
[TUNER]
button: FM 1
Procedure:
1. Tune the set to 97.9 MHz.
2. Connect the digital voltmeter to TP2 (SD) on MAIN board.
3. Adjust RV1 on TU100 so that the reading on the digital volt-
1. Tune the set to 97.9 MHz.
2. Connect the digital voltmeter to TP2 (SD) on MAIN board.
3. Adjust RV1 on TU100 so that the reading on the digital volt-
meter changes point from low to high.
Adjustment Location: See page 3.
TUNER SECTION
0 dB=1 µV
+
–
–
TP2 (SD)
MAIN board
digital
voltmeter
voltmeter
FM Stereo Separation Adjustment
Setting:
[TUNER]
button: FM1
Procedure:
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 28 dB
Adjustment Location: See page 3.
FM Stereo
Level meter
Level meter
signal generator
connection
reading (dB)
output channel
L-CH
L-CH
A
B
R-CH
L-CH
Adjust RV2 on TU100
for minimum reading.
R-CH
R-CH
C
D
L-CH
R-CH
Adjust RV2 on TU100
for minimum reading.
FM RF signal
generator
generator
Carrier frequency: 97.9 MHz
Output level: 22
Output level: 22
±
5 dB
Mode: mono
Modulation: 1 kHz, 22.5 kHz deviation (30%)
Modulation: 1 kHz, 22.5 kHz deviation (30%)
0.01
µ
F
set
antenna jack (CN900)
FM RF signal
generator
Carrier frequency : 97.9 MHz
Output level
Output level
: 74 dB
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%)
sub: 1 kHz, 33.75 kHz deviation (45%)
19 kHz pilot: 7.5 kHz deviation (10%)
0.01
µ
F
set
antenna jack (CN900)
+
–
–
speaker out terminal
level meter
4
Ω
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