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•t,.,
Service
Model
8672A
Table 8-2. Front
Panel
Status Annunciators
Annunciator
Name
OVEN
OUT
OF RANGE
REMOTE
STANDBY
NOT PHASE-LOCKED
INT
REFERENCE OFF
FM OVER MOD
ALC LEV UNCAL
Location
A2
A2
A2
A2
A2
A2
Al
Al
Purpose
Monitors
the reference oven
in the
A3
Assembly.
Indicates oven temperature
is
not stabilized.
Indicates
that
an
incorrect frequency
has been
programmed.
Indicates that the Synthesizer
is
in the
remote mode.
Indicates that the
LINE
switch
is
set
to
STANDBY.
Indicates that
one
or more
of
the loops
are
not;
phase-locked.
Refer to the
Phase
Lock Loop
Status Annunciators.
Indicates that the rear panel
FREQ
REF
switch
is
set
to
EXT.
Indicates that the
maximum FM
deviation
(A3)
or maximum
input drive
(Al)
has
been exceeded.
Indicates that the
ALC
(leveling) circuit
is
not providing
a
leveled
output or that the
range
attenuator
was programmed to
a
power
level
below
its range.
TROUBLESHOOTING
Begin troubleshooting by
following Table 8-3,
Overall Troubleshooting.
The
table
is
designed
to
isolate
a
malfunction
to
one
of
the three
major
assemblies. Begin
troubleshooting with
step
1. This
is
important
since
the table
assumes
that
all
mea¬
surements and indications are normal. When
a
mal¬
function
is
isolated
by
using
the table, turn to
the
service sheet
indicated
for further
troubleshooting
information.
The following information
can also
be used to
iso¬
late
a
malfunction to
the major assembly level
or it
can be used
as
supplemental information to the
table.
Refer to
Overall Troubleshooting Block Diagram.
Examine
the
front
and rear panel switches and
annunciators or program specific functions
and
examine
their
annunciators.
A
switch
or pro¬
grammed function
normally will effect only
one
annunciator.
Some
will
also
change
the
status
annunciators
listed in
the
Front
Panel Status
An¬
nunciators' table. Check
to
see
that
those related
to
the
malfunction
respond properly
to
the switch
setting or programmed
function. For
detailed
in¬
formation
on
the annunciator
response
to switch
settings, refer
to the
figures
showing the
front
and
8-30
rear panel
controls, connectors and indicators
in
Section
III.
Problems indicated by
the
NOT PHASE LOCKED
annunciator
can be
further
isolated by removing
the instrument's top
cover.
(Refer to the
Disassem¬
bly
and Reassembly procedures
in
this section.)
View
the phase-locked loop
annunciators
which
are
located on the
A2
assembly (refer to Figure
8-19).
If
the entire instrument
seems
to
be
off
or
if
the
STANDBY
annunciator
does
not
change
with
the
LINE
switch
being
set
to ON, check
the rear panel
fuse and
the power
supply and
thermal shutdown
annunciators. Also check the
+22
V
annunciator.
The next
step
is
to measure main
signal
paths
that
lead
to
a
malfunction
in one
of
the
major
assemb¬
lies.
Refer to the Overall Troubleshooting Block
Diagram. When
a
problem
is
isolated
to
a
major
assembly,
refer to
the
troubleshooting information
on
the appropriate
service sheet.
The following table
is
designed
to
isolate
a
mal¬
function to
one
of
three major
assemblies. Begin
troubleshooting with
step 1.
This
is
important,
since
the
table
is
set
up assuming that
all
previous
steps
are
normal. When
a
malfunction
is
located in
the table,
turn to
the service sheet indicated
for
further
troubleshooting information.
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