MCMartin.
2
T_he
amplified
RF
is
then fed
to
pin 1
of
IC-1
which
is
the
mixer
input. The
parallel
tuned
circuit
(L2,
C7,
and
CS)
establishes
internal
oscillator
frequency,
which
when
mixed
with
the input
signal
frequency, produces a 455
kHz
IF
frequency
at
the mixer output (pin 14 of
IC1
). C7
and
CS
insure
stable
operation
of
the
oscillator
within
ambient temperature
variations.
T2 provides
selectivity
prior
to
IF
amplification.
The
IF
amplifier
input appears
on
pin 7 of
IC-1.
The output (pin
6)
is
capacitive
coupled
to
pin 5, the AGC
drive
input,
and
also
connected
to
the tap of
T3.
T3 provides
addi-
tional
post
IF
selectivity
and through C18
drives
the
base
of
01.
01 is a common
emitter
gain
stage
which
in-
creases the
IF
signal
to
a
level
sufficient
to
drive
the
diode
detector.
02
is an
emitter
fol
lower
which
prevents
loading
of
01 by the
detector.
Diode
D1
serves as the AM
detector.
It
is
followed
by a low pass
filter
and an
audio
amplifier
stage
04.
05
is
connected as
an
emitter
follow-
er.
The
emitter
of
05
is
capacitive
coupled to the unbal.-
anced 600
ohm
output and
also
to the primary of
T5.
The
secondary
of
T5
is connected to the balanced 600
ohm
o-
utput.
termination.
D2 generates a negative
de
voltage
at
the base of
03
proportional
to
the
carrier
level.
03
will
be
biased in the •ott•
condition
as long as
carrier
is
present.
When
the
carrier
is
removed,
03
wil
I
be
switched
"on•,
energizing the c•
oil
of
carrier
fail
relay,
K1.
The
discrete
circuits
in the AMR-1 are powered from a
-+22
volt
de source, produced
by
a
full
wave
rectifier
and
an RC
filter.
IC-1 operates from a
+13
volt
de
supply,
regulated by
Z1,
and derived from the,+22
volt
de
supply.
V
TROUBLE
SHOOTING PROCEDURE
The AMR-1 has been aligned
at
the factory
to
conform
to
the published
specifications.All
tuned
circuits
have been
adjusted to provide maximum band-width and high
select-
ivity.
A perfect
field
alignment cannot
be
accomplished
without
proper
test
equipment, therefore,
if
this
is
de-
sired
it
is
recommended that the
unit
be
returned to the
factory.
However, the
AMR-1
can
be
aligned in the
field,
to
pro-
vide
satisfactory
operation,
with
the
following
proced-
ures:
Connect a volt-ohmeter to
test
point
"N'
located
on
the printed
circuit
board and
adjust
the meter
for
an
"on-scale"
positive
voltage reading.
Adjust
L2 for a
minimum
positive
voltage
at
test
point
"A".
If
a
dip
cannot
be
noticed
on
the meter when the
slug
of
L2 is
tuned, the
field
strength
at
the antenna input
may
be
too low. Tune
T1
and
L1,
in that order,
for
the same
condition
at
test
point
"A"
.Alternately,
tune T2 and
T3 for the minimum voltage
at
test
point
"A".
Repeat
the tuning of
L2,
T1,
and
L1
for
the same
test
condi-
tion.
The
AMR-1 should now
be
tuned
to
respond
to
the input
signal
frequency.
NOTE:
This
tuning procedure
will
result
in maximum
selectivity,
therefore, the 6
dB
bandwidth
speci-
fication
cannot
be
guaranteed
if
this
tuning pro-
cedure is used. Greater audio bandwidth can
be
obtained by
slightly
detuning
T1
and
L1.
In the event
of
malfunction,
check
the
following
symp-
toms and procedures:
A.
Carrier
fail
relay
will
not operate
1.
Check power
supply
voltage
2.
Short the
collector
of
03
to
ground and determine
if
relay
is
functional
3.
Check
03
and D2
4.
Check ~.,tenna input
RF
level.
It
should
be
a min-
imum of 100
microvolts.
B.
No
audio
output
1. Connect
VOM
to
test
point
"A"
and remove
an-
tenna. The voltage reading
on
the meter should
rise.
This
indicates
that
IC-1 is
working
properly.
a. Trace the
signal
through
01, 02,
D1,
04,
and
05
untiI trouble
is
located.
3.
Check power
supply
4.
Perform aIignment procedure
C.
Audio
output
distorted
1 •
Check
power
supply
voltage
2.
Insure
that
antenna input
is
not overloaded, by
re-
dueing antenna length.
3.
Perform aIignment procedure
D.
Noise in
audio
output
1 • Cheek a
11
grounds
2.
Antenna input
signal
level
Is
probably too
low,
In-
crease antenna
length.
E
.All
other problems should
be
referred
to
the
factory
by
contacting
the McMartin's Customer Service
Manager.
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