Fm Section - Sony RXD-700 Service Manual

0 dB = 1 µV

FM SECTION

Cautions during repair
When the front end is defective, replace it by a new one because
its internal block is difficult to repair.
FM Discriminator Adjustment
(NULL and MONO Distortion Adjustment)
Setting :
TUNER button : FM
FM ANTENNA
75 Ω COAXIAL
TAPE
FM RF SSG
REC OUT
set
Carrier frequency : 98.0 MHz
Output level : 60 dB (1 mV)
Mode : mono
Modulation : 1 kHz, 75 kHz deviation (100%)
TP701
NULL terminal
Procedure :
1. Tune the set to 98.0 MHz.
2. Adjust L702 for 0 ± 25 mV reading on the digital voltmeter.
............ NULL
3. Adjust L703 for a minimum reading on the distortion meter.
............ MONO Distortion (THD)
4. Repeat the adjustments of 2 and 3 several times.
Note : When replacing the ceramic filter, perform this adjustment.
Adjustment Location : See page 14.
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SECTION 3
DISASSEMBLY
FM Stereo Separation Adjustment
Setting :
1 kHz
high pass
distortion meter
filter
Procedure :
digital voltmeter
(DC range)
L-CH stereo separation : A – B
R-CH stereo separation : C – D
The separations of both channels should be equal.
Adjustment Location : See page 14.
FM Tuning Level Adjustment
Setting :
Procedure :
1. Tune the set to 98.0 MHz.
2. Adjust VR701 so that the TUNED indicator goes on.
3. Confirm that the TUNED indicator goes off with FM RF SSG
Adjustment Location : See page 14.
– 12 –
TUNER button : FM
FM ANTENNA
75 Ω COAXIAL
FM RF SSG
Carrier frequency : 98.0 MHz
Output level : 60 dB (1 mV)
Mode : stereo
Modulation : main : 1 kHz, 37.5 kHz deviation (50%)
sub : 1 kHz, 37.5 kHz deviation (50%)
19 kHz pilot : 6.75 kHz deviation (9%)
FM stereo
Level meter
signal generator
connection
output channel
L-CH L-CH
R-CH L-CH
R-CH R-CH
L-CH R-CH
TUNER button : FM
FM ANTENNA
FM RF SSG
75 Ω COAXIAL
Carrier frequency : 98.0 MHz
: 25 dB (17.8 µ V)
Output level
Mode : mono
Modulation : no modulation
output level set at 22 dB.
TAPE
level meter
REC OUT
set
Level meter
reading (dB)
A
B
Adjust VR703 for minimum
reading on level meter.
C
D
Adjust VR703 for minimum
reading on level meter.
set