Sharp GF-320A - FM IF;RF ADJUSTMENT; FM Tuning and Alignment; VCO FREQUENCY ADJUSTMENT; Frequency Calibration

FM IF/RF ADJUSTMENT
10.7 MHz Oscilloscope
FM mono
I
WITCH
?OSITION
SIGNAL
GENERATOR
400 Hz, 30%. FM modulated.
-
;TEP
I 1
I 1
TEST
STAGE
AD-
JUST-
MENT
Tl
REMARKS
1. Using a minus
driver, turn
the core of
T2 counter-
clockwise
before taking
it out of the
bobbin.
2. Adjust for
best “IF”
curve.
Adjust for best
“S” curve.
Figure 7-l FM IF
-Y- -%f
1
IF
10
.7 MHz High
frequency
Figure 7-2 IF CURVE
Figure 7-3 FM S CURVE
Detection T2
Electronic
Repeat steps 1 and 2 until no further improvement can
/
1
FM Signal
External
Voltmeter
Rod Antenna
Generator
Speaker
t
1
I~ ,( Terminal
‘I
Unit
be made.
Band
frequency
coverage
109 MHz
Highest
TC2
maximal output.
1
frequency
Repeat steps 4 and 5 until no further improvement can
be made.
88 MHz 88MHz L2 Adjust for
Trackmg maximal
108 MHz 108 MHz
TCl output.
Repeat steps 7 and 8 until no further improvement can
be made.
5
Dummy
(See Figure 7-6)
6
-
7
Figure 74 FM RF
Electronic
B
FM Signal
Generator
Rod Antenna
I
9
7
VCO FREQUENCY ADJUSTMENT
Dummy
(See Figure 7-6)
GN/D
SIGNAL
I
400 Hz, 30%. FM modulated
GENERATOR
(mono signal)
I
Figure 7-5 VCO FREQUENCY
A
To Telescopic Rod Antenna
R2
FM mono position
98 MHz at
98 MHz
60 dB
FM stereo position (unmodulated)
VRl
Adjust for
38.00 kHz + 100 Hz.
To Chassis GND
Rl = 500hms
z = 5o OhmsLR2 = 5. ohms
2: Output impedance of signal generator
Figure 7-6 FM DUMMY
-7-