Scott 325R Service Manual

SCOTT 325R/335R
FM IF Amplifier
To pin 11
of!C301
0
Shei/ded
L2
Coax Cable
0
3 turn coil
0
0 0
To chassis
ground
I) Mute the FM local oscillator by shorting IA.
2) Connect the oscilloscope to pin 11 of IC301.
3) Apply 10.7
MHz
signal from the sweep generator to L2
in the manner as shown above.
4) Adjust L201 for correct figure as shown. It may be neces-
sary to increase or decrease the sweep generator output for
adjustment convenience.
FM RF Tracking
--I
1S446, etc.
'
,,
470k
ohm
I
I
I
I
I
I
___ .,_. _ _ _ _ ....,I
' - - - - - - -.J
Correcc
111 ffJ
Oa
FM
Dummy
Ant
.------,Tape/Rec
[2J
Out
FM Signal
Generator
o:.=====i
FM Ant
300Ohm
I) Apply 90 MHz , I kHz and I 00% modulated, 25 dBf signal
level to the FM antenna terminals.
2) Tune the unit to 90 MHz.
3) Observe the oscilloscope connected to the Tape/Rec output
terminal for symmetrical sine wave.
If
failed, adjust
IA.
4) Adjust LI and L2 for maximum level meter reading. Re-
duce input from the 25 dBf level as necessary to maintain
noise on sine wave.
5) Readjust the ·signal generator for I 06 MHz, and retune unit.
6) Repeat step 3.
If
failed, adjust the OSC. trimming capacitor
mounted on the tuning capacitor.
7) Adjust the trimming capacitors, for mixer and RF.
8) Repeat as necessary until product specifications are met.
Level Meter
DJ
Distortion Analyzer
0.001µF
Oscilloscope
Incorrect,
as
coo low
Oscilloscope
lncorrecc,
as too narrow