Adjustment - Sharp QT-90W Service Manual

QT-90W
TUNER SECTION
fL: Low-range frequency
fH: High-range frequency
Step Alignment
Frequency
1 FM IF: (1) FM IF sweep
10.7 MHz
(2) Alignment
(T108)
FM
DETECTION: (3) Power supply
(T106)
2 FM BAND (1) FM RF sweep
COVERAGE fH:
108.2 MHz (2) Alignment
(3) Power supply
3 FM BAND Same as step 2
COVERAGE fL:
87.4 MHz
4 Repeat step 2, 3 until no further improvement can be made.
5 FM TRACKING Same as step 2
fH: 106 MHz
6 FM TRACKING Same as step 2
fL: 90 MHz
7 Repeat step 5, 6 and then step 2, 3, 5, 6 until no further improvement can be made.
Step Alignment
Frequency
1 VCO: 75 kHz (1) Frequency counter Inject MONO
(2) Power supply
(3) FM Signal
Pin 13 of IC102
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ADJUSTMENT

FM Section
Test Equipment Signal-in
Inject the IF
generator sweep signal
through 300 pF
oscilloscope capacitor to point
TP2
Inject the RF
generator signal directly to
point TP1
oscilloscope
Same as step 2
Same as step 2
Same as step 2
FM Stereo Section
Signal-in
Test Equipment
signal at 98 MHz
directly to point
generator TP1 and ground
Pin 21 of IC102
G
10 pF
1M ohm
10K ohm
Signal-out
Signal are taken Adjust T106, T108
out from point TP3 and repeat to get
best "S" curve with
center at 10.7 MHz
Same as step 1 Adjust P.V.C. (TC1)
get MAX. output
Same as step 1 Adjust L103 to get
MAX. output
Same as step 1 Adjust P.V.C. (TC2) to
get MAX. output
Same as step 1 Adjust L102 to get MAX.
output
Signal-out
Through test Adjust VR102 let
circuit as Fig 6. Frequency counter
value: 76 K ± 200 Hz.
D
FET: 2SK212
(or other 2SK type FET.)
S
0.1 µF
Figure 6
– 6 –
Adjust Remark
(1) Band SW in FM.
(2) VOL. & TONE
control in MIN.
position
(3) Tune P.V.C. to
high end
Same as step 1
Tune P.V.C. to low
end
Tune P.V.C. to
106 MHz
Tune P.V.C. to
90 MHz
Remark
Adjust
(1) FM and stereo
position
(2) Tune radio to
98 MHz
To frequency
counter