HP 8340b User Manual

M/N
Loop
Assembly-Level
Troubleshooting
The
following troubleshooting
procedure
provides
information for
isolating
an
M/N
loop
failure to
the
assembly
level.
The
assemblies
which
are
covered
in
this
procedure
are:
A31
M/N
phase
detector assembly
A32
M/N
VCO
assembly
A33
M/N
output
assembly
A34
reference
loop
—
M/N
loop
motherboard
A59
digital
interface
assembly
During
troubleshooting,
refer to Figure
B-21,
M/N
Loop Troubleshooting
Block
Diagram.
When
an
output
signal
level
is
not
mentioned
in
the
troubleshooting
procedure,
refer
to Figure
B-21
for
the
required level.
Also
provided
in
this
section
are
the
spectrum
analyzer
plots
of
the M/N
Loop output
signals
(Figures
B-13
through B-20).
M/N
VERIFICATION AND
LOW
OUTPUT
POWER TROUBLESHOOTING
NOTE:
Before
replacing
A31, A32,
or
A33,
remove
the
assembly from
the
instrument
and
verify
that
the
appropriate
power
supply voltages
are
present
at
the
assembly's
input. Refer
to
the
end of
the
Service
Introduction
in
this
manual.
For
the
A31
and
A33
assemblies,
a
missing
power
supply
is
due
to
either
a
failure
on
the
A34
reference
loop
—
M/N
loop
motherboard
or
a
failure
in
the
power
supplies.
In
the
case
of
A32,
a
missing
power
supply
can
also
be
due
to
a
failure
on
the
A33
assembly.
This
verification
is
to
determine
if
the
M/N
Loop outputs
the
correct
M/N
OUT
signal
(frequency
and
power
level)
over
the
entire
range
of
its
internal
dividers.
If
you
have already determined
a
CW
frequency
that
generates
an
incorrect
M/N
output
frequency,
you
don't
need
to
perform
this
verifica¬
tion.
Proceed
to step
1
of
the
M/N
Output
Frequency
Incorrect troubleshooting,
below.
If
you
are
not
sure
which
CW
frequency
causes
the
incorrect
M/N
OUT
signal,
proceed
with
step
1
of the
verifica¬
tion.
NOTE:
Pressing
[SHIFT]
[M1]
displays,
from
left
to
right:
M
Divide
N
Divide
M/N
OUTput
20/30
OUTput
Number Number
Frequency
(MHz)
Frequency
(MHz)
NOTE:
In
the
following
procedure,
the
acronym
DUT
(device
under
test)
is
used
to
describe
the
instrument
you
are
troubleshooting.
1. Connect
the
frequency
counter's
PREQ
STD
OUT
to
the
DUT's
rear
panel
EXT
FREQUENCY
STANDARD
input.
Switch
the DUT's
FREQUENCY STANDARD
switch to
the
EXT
position
(the
EXT
REF
annunciator
should
be
on).
2.
Disconnect
the
SMB
cable
from
A33J2
and
connect
the
frequency
counter's
10
Hz
—
500
MHz
input
to A33J2.
HP
8340B/41B
M/N
Loop Assembly-Level
Troubleshooting B-21

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English