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.
SECTION 3
DISASSEMBLY
1 kHz
high pass
distortion meter
filter
digital voltmeter
(DC range)
– 12 –
FM Stereo Separation Adjustment
Setting :
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%)
Procedure :
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
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 :
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
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
output level set at 22 dB.
Adjustment Location : See page 14.
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