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FM TUNER ALIGNMENT |
FM ALIGNMENT — FUNCTION switch to FM STEREO
Standard test frequency 1 kHz and deviation +75kHz
ITEM
GENERATOR
' |
DIAL SETTING
INDICATOR
PROCEDURE
Note: The FM IF circuit utilizes a non-turnable ceramic filter which establishes the IF bandpass. To insure symmetrical
turning and selectivity, the IF must be aligned precisely to the center of the filter bandpass, rather than to 10.7MHz
as in conventional LC circuits.
1. FMIF
Connect 10.7MHz Radio | Position of
Connect Radio IF
Adjust FM IFT (T1) and FM DET
S-CURVE
IF Genescope output to | non-interference
Genescope input
| Coil (T2) until the S-curve
ALIGNMENT
TP1 and ground terminal.)
Minimum
to TP2 and ground
| becomes symmetrical and
Use
10~20pF Capacitor | Frequency.
terminal.
_ |
Straight.
in series with generator
lead.
. FRONT END
Tuning knob fully
Place center of dial pointer on "0"
ALIGNMENT
counterclockwise.
(zero) and secure pointer with
bonding material.
. FM RF
Connect FM RF Signal
Center of 87MHz
Connect AC VTVM, | Adjust FM OSC Coil (L6) and FM
TRACKING
Generator through FM
calibration mark
Distortion Meter
ANT Coil (L5) for best curve form
ALIGNMENT
Dummy Antenna toFM
on dial.
and Oscilloscope
j|.and minimum distortion.
(87MHz)
Antenna terminals.
to TP2 and ground
Set generator to 87MHz.
terminal.
Modulate with 1kHz to
provide +75kHz
deviation.
Set generator output
with attenuator as low
as possible.
4.
Change generator
Center of 1\O9MHz | Sameas above.
.
Adjust FM OSC Trimmer (TC2)
(109MHz)
Setting to 109MHz.
calibration mark
and FM ANT Trimmer (TC1) for
on dial.
best curve form and deflection.
Note: Repeat Items 3 and 4, and confirm that Tracking Error is minimized and best sensitivity is obtained at each frequency
point. Then, set generator to 98MHz and confirm that the pointer is correctly set on the dial plate.
. DETECTOR
Connect FM PF Signal
Center of 98MHz
Connect Harmonic | Adjust FM DET (T2) for minimum
ADJUST-
Generator to FM ANT
calibration mark
Distortion Meter
gain and best linearity.
MENT
terminals.
on dial.
and Oscilloscope
(MINIMUM
Set generator output
to TP2 and ground
T.H.D.)
level to 60GB at
terminal.
98MHz +2kHz.
. PLL IC
Same as above.
Same as above.
Connect 3900
Adjust VR1 in multiplex circuit
FREE RUN
Resistor and Fre-
to obtain 38kKHz +200Hz on
FREQUENCY
quency Counter
Frequency Counter.
ADJUST-
between IC5 (Pin
MENT
No.6) and ground
(19kHz)
terminal.
Use a screwdriver with plastic grip for all adjustments.
=4g—
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