Fm Adjustment; Before Adjustment; Connection Diagram (Measuring Instruments) - Yamaha RX-V795a Service Manual

RX-V795a/RDS/HTR-5170

FM Adjustment

Before Adjustment

1) For dB, 1µV=0dBµ
Example : 60dBµ=1mV
2) 100% modulation means that the frequency deviation is
± 75kHz.

Connection diagram (Measuring instruments)

1) Discriminator balance adjustment
FM
FM
dummy
SG
antenna
Oscillator
2) Monaural distortion adjustment
FM
ANT
FM
FM
dummy
SG
GND
antenna
Oscillator
Adjustment item
Step
Rough adjustment of
1
discriminator balance
Rough adjustment of
2
monaural distortion
Fine adjustment of
3
discriminator balance
Fine adjustment of
4
monaural distortion
Verification of dis-
5
criminator balance
* : Execution of FACTORY PRESET (Refer to page 16.) will facilitate setting reception frequency for adjustment.
** Must be 98.1MHz ± 5kHz
23
TP1
FM
ANT
TUNER
DCVM
P. C. B.
GND
TP2
L
Oscilloscope
R
TUNER
P. C. B.
REC
OUT
DIST. M
Reception
Signal (ANT IN)
frequency
98.1MHz
FM ANT (75Ω)
* (A-4)
98.1MHz **
70dBµ
MONO 100Hz
100% modulation
98.1MHz
Same as Step 1.
* (A-4)
98.1MHz
Same as Step 1.
* (A-4)
98.1MHz
Same as Step 1.
* (A-4)
98.1MHz
Same as Step 1.
* (A-4)
3) Install the Matching Transformer and connect FM SG.
4) Set each switch to the following position unless other-
wise specified.
INPUT SELECTOR .................. TUNER
TUNING MODE ....................... AUTO
3) Stereo distortion adjustment/separation adjustment
FM
ANT
FM
TUNER
FM
dummy
P. C.. B.
SG
GND
antenna
SSG
4) Sensitivity Verification
FM
ANT
FM
FM
dummy
SG
GND
antenna
Adjustment
Test point
point
Both ends of R25
T1
(Between TP1 and TP2)
(IC1 side core)
REC OUT L, R
T1
(TE1 side core)
Both ends of R25
T1
(Between TP1 and TP2)
(IC1 side core)
REC OUT L, R
T1
(TE1 side core)
Both ends of R25
T1
(Between TP1 and TP2)
(IC1 side core)
L
Oscilloscope
R
YLF-15
REC
(LPF)
ACVM
OUT
DIST. M
L
Oscilloscope
TUNER R
P. C. B.
REC
ACVM
OUT
DIST. M
Rating
DC 0V±100mV
Minimize the dis-
tortion.
DC 0V±50mV
Minimize the dis-
tortion (to 43dB
or less).
DC 0V±50mV