Adjustment - Sharp QT-80W Service Manual

TUNER SECTION
fL: Low-range frequency
fH: High-range frequency
Step
Alignment
Frequency
1 FM IF:
10.7 MHz
(T108)
FM
DETECTION:
(T106)
2 FM BAND
COVERAGE fH:
108.2 MHz
3 FM BAND
COVERAGE fL:
87.4 MHz
4 Repeat step 2, 3 until no further improvement can be made.
5 FM TRACKING
fH: 106 MHz
6 FM TRACKING
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
Pin 13 of IC102

ADJUSTMENT

Test Equipment Signal-in
(1) FM IF sweep Inject the IF
generator sweep signal
(2) Alignment through 300 pF
oscilloscope capacitor to point
(3) Power supply TP2
(1) FM RF sweep Inject the RF
generator signal directly to
(2) Alignment point TP1
oscilloscope
(3) Power supply
Same as step 2 Same as step 2
Same as step 2 Same as step 2
Same as step 2 Same as step 2
FM Stereo Section
Signal-in
Test Equipment
(1) Frequency counter Inject MONO
(2) Power supply
signal at 98 MHz
(3) FM Signal directly to point
generator TP1 and ground
G
10pF
1M ohm
10K ohm
FM Section
Signal-out
Signal are taken
out from point TP3 and repeat to get
Same as step 1
Same as step 1
Same as step 1
Same as step 1
Signal-out
Through test
circuit as Fig 7.
Pin 21 of IC102
D
FET 2SK212
(or other 2SK type FET)
S
0.1
F
Figure 7
– 7 –
Adjust
Adjust T106, T108 (1) Band SW in FM.
(2) VOL. & TONE
best "S" curve with control in MIN.
center at 10.7 MHz position
(3) Tune P.V.C. to
high end
Adjust P.V.C. (TC1) Same as step 1
get MAX. output
Tune P.V.C. to low
Adjust L103 to get
MAX. output end
Adjust P.V.C. (TC2) to Tune P.V.C. to
get MAX. output 106 MHz
Adjust L102 to get MAX. Tune P.V.C. to
output 90 MHz
Adjust
Adjust VR102 let (1) FM and stereo
Frequency counter position
value: 76 K ± 200 Hz.
(2) Tune radio to
98 MHz
To frequency
counter
QT-80W
Remark
Remark