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GF-7850H(D)
©
FM IF/RF ADJUSTMENT
SWITCH
POSITION
SIGNAL
400Hz, 30%, FM modulated
GENERATOR
1. Using a minus
driver, turn
the core of
T2 counter-
clockwise
before taking
it out of the
bobbin.
. Adjust for
best "IF''
curve.
Adjust for best
"S'' curve.
Adjust for
maximal
output.
Repeat steps 4, 5 and 6, 7 until no further improvement can
33
VCO FREQUENCY ADJUSTMENT
SIGNAL
400 Hz, 30%, FM modulated
GENERATOR | (mono signal)
DIAL
FREQUENCY | POINTER
| ADJUST-
SETTING
MENT
FM mono position
FM stereo position
(unmodulated)
98 MHz at
VRi
Adjust for
60 dB
38.00 kHz + 100 Hz.
10.7 MHz
FM sweep
generator
Oscilloscope
C1
0.01 uF @ PIN
Figure 14-1
FM IF
10.7 MHz
10.7 MHz
Figure 14—2
IF CURVE
Figure 14—3 S CURVE
Electronic
External
voltmeter
FM signal
speaker
generator
Rod antenna
©
-
j
ca
terminal
-
GND
GND
-
Dummy
(See Figure 14—6)
Figure 14-4 FM RF
IC3
FM signal
Rod
© PIN
Frequency
antenna
generator
1000 pF
counter
Dummy
(See Figure 14-6)
Figure 14-5 VCO FREQUENCY
R1
To Telescopic rod antenna
Pr
"
(Zz
i
R2
iO
cf
To chassis GND
_
R1 = 37.5 ohms
Z= 75 ohms<—_5o = 76 ohms
_
R1 = 50 ohms
mate ohms<
po = 50 ohms
Z: Output impedance of signal generator
Figure 14-6 FM DUMMY
-14—
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