HP 8340b User Manual

Sweep
Generator
Assembly-Level
Troubleshooting
INTRODUCTION
There
are
two
basic
failure modes
that
have
to
do
with
the
sweep
function
of the
instrument.
•
The
instrument
is
not
sweeping.
•
The
instrument
is
sweeping,
but
the
sweep
is
incorrect
—
the
frequency
limits
of
the
sweep
are
wrong and/or bandcrossings
are
not
occurring.
The
first
task
is
to
get
the
instrument
to
do repetitive
sweeps
of
any
kind.
If
the
MARKER RAMP
(ASS
TP4)
is
sweeping
zero
to
ten
volts and
the
front panel
sweep
LED
is
blinking,
the
instrument
is
considered to
be
sweeping
even
though
the
output frequency
may
not
be
moving.
If,
on
the
other
hand,
MARKER
RAMP
is
stuck and
the
front
panel
sweep
LED
is
continuously
on
or
off,
the
instrument
is
not
considered
to
be
sweeping.
When
looking
at
the
LED, care must
be
taken
because
in
fast
sweeps
it
may
appear
to
be
on
all
the
time,
even
though
it
Is
actually
blinking.
NO
SWEEP
Assuming
that
the
instrument
processor
is
functioning
correctly,
the
only
external
lines that
can
prevent
the
ASS
sweep
generator
from
sweeping are
HSP
(high
sweep,
A58P1-13),
LBX
(low
band-
cross,
A58TP6)
and
LRSP
(low
reset
sweep,
A58TP11).
HSP
and
LRSP
are
standard
TTL
lines
with
HSP
being
driven
by
the
A57
marker/bandcross
assembly
and
LRSP
being driven
by
the
A59
digital
interface
assembly.
LBX
is
an
open
collector
line that
can
be
driven
by
both
the
ASS
sweep
generator
and
A57
marker/bandcross
boards.
HSP
is
coupled
to
LBX
on
the A57
marker/bandcross
assembly
so
that
if
LBX is
pulled
down,
the
A57
marker/bandcross
assembly
pulls
down
on
HSP
also.
If
the
instrument
is in
the
continuous
sweep
mode
and
is
not
sweeping,
remove
the
A57
marker/
bandcross
assembly.
If
the
instrument
now
sweeps,
the
problem
is
most
likely
on
the
A57
marker/
bandcross
assembly
(in
the
controller
section).
Note
that
in this
mode,
the
frequency
limits
that
the
instrument
is
sweeping
over
will
not
be
correct.
This
is
because
it
is
the
A58
sweep
generator
that
is
pulling LBX
low to
stop
the
sweep
when
the
MARKER
RAMP
reaches
12
volts.
If
the
instrument
still
will
not
sweep
with
the
A57
marker/bandcross assembly
removed,
place
the
A58
assembly
on
an
extender
board and
check
the
state
of
the
HSP
line,
A58P1-13.
Since
only
the
A57
marker/bandcross
assembly
can
pull
down
on
this
line,
it
should
be
high
in
this
mode.
If it
is
low,
troubleshoot
this
problem.
If
HSP
is high,
check
the
state
of
LBX
(A585TP6).
If
it
is
low,
determine
what
is
pulling
it
low
by
looking at
HBX
(A58TP5).
If
HBX
is
high,
the
A58
sweep generator
is
faulty,
and
is
pulling
down on
LBX.
If
HBX
is
low,
troubleshoot
the
A59
digital
interface
(in
the
Controller
Section).
Finally,
look
at LRSP,
A58TP11.
If
it
is
stuck
low,
check
it
at
its
source
—
the
A59
digital
interface
assembly.
If
the
three lines
Just
discussed,
LBX,
HSP
and
LRSP
are
all high,
the
problem
is
indeed
on
the
sweep
generator assembly.
Reinstall
the
marker/bandcross
assembly. Replace
the
A58
sweep
generator
assembly
or
consult
the
A58
troubleshooting
section
in
the
optional
Component
Level
Service Manual
set
if
component
level
repair
is
intended.
D-24 Sweep
Generator Assembly-Level
Troubleshooting
HP
8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English