HP 8340b User Manual

RF
Section
Overall
Assembly-Level
Troubleshooting
Begin
initial
instrument
troubleshooting
in
the
service
introduction
section.
Once
you
isolate the
prob¬
lem
to
the
RF
section,
the
troubleshooting
in
this
section
can
be
broken
into
three
areas:
•
SYTM
peaking
Peaking
is
a
function
designed
to
tune
the
SYTM
so
that
the
RF
output
is
in the
center
of
the
SYTM
passband,
ensuring
that
maximum
RF
power
is
available. Use
the
SHIFT
MANUAL
sweep
diag¬
nostic
to troubleshoot
the
peaking
function.
•
ALC
loop
The
ALC
loop
is
a
feedback control
system
that
monitors
RF
power
and maintains
that
power
at
a
set level.
A
voltage
representing
the
RF
power
level
is
detected (internally
or
externally) and
compared
to
a
reference level.
If
the
levels
are unbalanced,
the
ALC circuitry
drives
the
modu¬
lators
and
varies
the
RF
output
until
the
voltage levels
balance.
Use
the
SHIFT
METER
diagnostic
to
open
the
ALC
loop
for
troubleshooting.
•
RF
path
The
RF
path
consists
of
14 RF
microcircuits and
their
associated
bias
assemblies.
To
trou¬
bleshoot
the
RF
path,
initialize
the
instrument to
a
known state
and
measure
the
RF
power
levels
at
various junctions
in
the
path.
Minimum
power
levels
are
provided for
each
microcircuit
on
the
RF
path
troubleshooting
block
diagram.
TROUBLESHOOTING
SEQUENCE
Troubleshoot
the
RF
section
in
an
ordered
sequence
to systematically
isolate
assemblies:
1.
SYTM
peaking
problems
2.
ALC
loop
problems
3.
RF
path
problems
Each
troubleshooting
sequence
leads to the
next.
What
may
appear
to
be
an
ALC
loop
fault,
for
example,
may
actually be
an
RF
path
(microcircuit)
failure.
By
completing
the
ALC
loop
diagnostics,
the
RF
path
failure
is
indicated, leading
you
to
the
RF
path troubleshooting
procedures.
HP
8340B/41B
RF
Section
Overall Assembly-Level
Troubleshooting
H-15/H-16

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English