Fisher FM-120L - Page 5

AM-FM MULTIPLEX ALIGNMENT
“AM
ALIGNMENT
For
alignment:
Maintain
generator
output
as
low
as
possible
for
suitable
indication.
i
Connection
.
Adjusting
Position
of
V.T.V.M.
circuit
Tuning
dial
Oscilloscope
Near max. capa-
rrT iT PIV It
city of VC at AM IFT
position of no 2-00040
interference
Connect 455 kHz sweep
generator to VC4.
Connect Oscilloscope
to Test Point TP6.
a
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Connect AM generator to
AM BAR ANT
EXT
AM
antenna
and
GND
acorn
9-25240
terminals.
Set
to
600
kHz.
.
MW
OSC
Modulate
with
30
%,
400
Hz.
Connect
Oscilloscope
and
.
9-20851
AC. V.T.V.M. to
Tuner Output.
Change frequency to 1400 kHz.
1400 kHz TC 01,03
Change frequency to 160 kHz.
LW (RF)
160 kHz Lw OSC 9-20860 |
350 kHz TC 02,04
1.
Variable
capacitor
completely
closed
4
Function
switch
to
“MW"
or
“LW”
2.
Set
the
dial
pointer
to
very
left
line
dial
scale.
5.
Use
a
screwdriver
with
plastic
grip
for
all
adjustments.
3
Connect
sweep
generator,
SG,
V.T.V.M.
and
oscilloscope.
Adjustment
FM
ALIGNMENT
|
|
|
FM
SFT
FM
QUAD-
;
Connect Oscilloscope
to Test Point TP4
RATURE COIL
9-21320
V.T.V.M.
Oscilloscope
Position of
Adjusting
Tuning dial
circuit
Near max. capa-
city of VC. at
position of no-
interference
Connect sweep 10.7 MHz
generator to test poin
VC2.
Connect Oscilloscope
to Test Point TP3
Quadrature
Detector
Connect FM RF generator through
two
120-ohm
resistors
to
FM
ANT
COIL
FM
antenna
screw
terminals.
9-21180
Set
generator
to
90
MHz,
FM
RF
COIL
modulate
with
400
Hz
to
provide
Connect
V.T.V.M.
9-20460
£75
kHz
deviation.
Set
generator
to
Tuner
Output.
EM
OSC
COIL
output
attenuator
as
low
as
9-20910
possible.
_ Change generator setting
to 106 MHz.
Repeat
adjustments.
106 MHz
1.
Variable
capacitor
completely
closed
_
4.
Function
switch
to
“FM”
|
2.
Set
the
dial
pointer
to
very
left
line
of
dial
scale.
5.
Use
a
screwdriver
with
plastic
grip
for
all
adjustments.
3
Connect
sweep
generator,
FM
SG,
V.T.V.M.
and
Adjustment
Adjust VRO4 (5k-B) so that
frequency counter or synchroscope
indicates 19 kHz.
Near max. capa-
city of VC. at
position of no
interference
VROS (1k-B)
1.
Variable
capacitor
completely
closed
|
3.
Function
switch
to
“FM”
2.
Connect
FM
stereo
SG
and
V.T.V.M.
4,
Use
a
screwdriver
with
plastic
grip
for
all
adjustments.
oscilloscope.
FM
ANT
input
impedance
is
75
ohm.
ALIGNMENT
: :
ee
: ; -Connect Frequency
None .
FM MPX
Position of
Adjusting
Tuning dial
circuit
counter or synchro-
scope to TP5 |
FO (19 kHz)
Adjustmnet
Connect V.T.V.M. to
output terminal |
{R Channel)
As above Steps 3,4 except
modulation. Modulate LEFT
channel +67.5 kHz — 400 Hz
audio and +7.5 kHz — 19 kHz
pilot carrier.
As above except modulate
RIGHT Channel.
FM STEREO
Signal
Separation
Connect V.T.V.M. to
output terminal
{L Channel}.
Repeat
steps
1,2.
Set
at
position
with
max.
channel!
separation.
a or