
Check
1st
LO
Signal
at
Sampler/Mixer
If
the
4
kHz
signal
is
badat
the
sampler/mixer
assem
bly
,
c
hec
k
the
1st
LO
signal
where
it
en
ters
the
sampler/mixer
assem
bly
in
question.
If
the
1st
LO
is
fault
y
,
c
hec
k
the
1st
LO
signal
at
its
output
connector
on
the
A7
assem
bly
to
determine
if
the
failure
is
in
the
cable
or
the
assem
bly
.
If
the
1st
LO
is
go
o d,
con
tinue
with
\Chec
k
2nd
LO
Signal
at
Sampler/Mixer."
Check
2nd
LO
Signal
at
Sampler/Mixer
Chec
k
the
2nd
LO
signal
at
the
pins
iden
tied
in
T
able
8-3 .
Refer
to
the
\A12
Reference
Chec
k"
in
Chapter
7,
\Source
T
roublesho oting,"
for
analog
bus
and
oscilloscop
e
c
hec
ks
of
the
2nd
LO
and
w
a
v
eform
illustrations.
T
able
8-3
iden
ties
the
signal
lo
cation
at
the
samplers
and
the
A12
assem
bly
.
T
able
8-3.
2nd
LO
Locations
Mnemonic
Description
Sampler
Lo cation
Signal
Source
2nd
LO
1
2nd
LO
(0
degrees)
A4/5/6
P1-11
A12P1-2,
32
2nd
LO
2
2nd
LO
( 090
degrees)
A4/5/6
P1-4
A12P1-4,
34
If
the
2nd
LO
is
go
o d
at
the
sampler/mixer,
the
sampler/mixer
assem
bly
is
faulty
.
Otherwise,
troublesho
ot
the
A12
assem
bly
and
asso
ciatedsignal
path.
8-10
Receiv
er
Troubleshooting
DRAFT
3/21/106
15:13
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