HP 8340b User Manual

YO
Loop
Assembly-Level
Troubleshooting
INTRODUCTION
The
YO
UNLOCKED
error
condition
can
be
caused
by
a
number
of
different
failures.
Figure
D-5,
YO
Loop
Troubleshooting
Flow
Chart,
provides
a
systematic
way
to
identify
the
malfunctioning
assembly.
Also
refer
to
Figure
D-4,
Sweep
Generator
and
YO
Loop
Simplified
Block
Diagram.
Each
of
the
following
headings
refer
to
the
Troubleshooting
Flow
Chart
and
assumes
that
the
front panel
UNLK
indicator
is
on.
Power
levels
are
shown on
Figure
D-6.
Sweep
Generator
and
YO
Loop
Troubleshooting
Block
Dia¬
gram.
YO UNLK
-
CW/MANUAL MODE
NOTE:
The
[SHIFT] [M4]
diagnostic
can
help isolate the
cause
of
an
UNLK
condition.
Use
this
diagnostic
feature
after
performing
the
troubleshooting
procedure
shown
below.
Refer
to
the
overall
instrument
troubleshooting
section
in
the
service
introduction
for details.The instrument
UNLK
diag¬
nostics
can
be selected
by
pressing
[SHIFT]
[EXT]
on
the
front
panel.
This
will
display
the
following:
OSC: REF
M/N
HET
YO N2
N1
A
YO
unlock
condition
exists
when
the
"YO"
indicator
is
flashing.
In
most
cases,
the
error
condition
will
occur
in
the
CW/MANUAL
mode,
and
the
troubleshooting
should
be
done
in
this
mode
first.
If
the
YO
loop
will
not
phase-lock
in
CW/MANUAL at
all
frequencies,
it
will
not
function
properly
in
the
SWEPT
mode.
To
troubleshoot
in
the
CW/MANUAL
mode,
perform
the
following
steps.
Refer
to
Figure
D-5:
1.
Are
Other
Loops
Locked?
Check
to
see
that the
UNLK
indicators for
the
REF,
M/N, N2,
and
N1
loops
are
not
flashing.
If
these other
loops
are
unlocked,
the
YO
loop
will
not
function
correctly.
Troubleshoot
the
other
loops first.
If
they
are
all
locked,
proceed to question
2.
2.
Is
Front Panel
RF
Power
Correct?
Check
that
RF
is
present
at the
front
panel
at
a
level
close
to
the
selected
power.
If
not,
there
is
a
problem
in
the
RF
path
—
go
to question
14.
If
the front
panel
RF
is
present
at
the
correct
power,
proceed
to
question
3.
HP
8340B/41B
YO
Loop
Assembly-Level
Troubleshooting
D-15

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English