HP 8340b User Manual

16.
Is
the
YO
Main
Coil
Drive
Correct?
Check
the
YO MAIN COIL
DRIVE.
This
can
be
done
by
testing
the
SENSE
voltage,
TP4
on
the
ASS
YO
driver
assembly.
(The
SENSE
voltage
is
related
to
the
YO
frequency
by
-2.4
V/GHz.)
If
the
YO
main
coil
is
greatly
mistuned, no
YO
signal
will be
present.
If
the
SENSE
voltage
(hence
the
YO
MAIN
COIL
DRIVE
current)
is
correct
to
within
±1V,
troubleshoot
the
YO;
if
not,
proceed
to
question
17.
17.
Is
the
PRETUNE
Voltage
Correct?
This
portion
of
the
troubleshooting
guide
is
a
branch
from question
3,
question
10,
and question
16.
Check the
PRETUNE
voltage.
PRETUNE
has
a
sensitivity
of
-2.5
V/GHz of
YO
frequency.
If
the
PRETUNE
voltage
is
correct,
troubleshoot
the
ASS
YO
driver
(OFFSET
and
GAIN)
and
the
A47
sense
resistor
assembly.
If
PRETUNE
is
not
correct,
proceed
to
question
18.
18.
Is
the
VSWP
Voltage Correct?
Check
that
the
VSWP
voltage
is
zero
volts.
If it
is
correct,
suspect
the
AS4
YO
pretune/delay
compensation
assembly.
If
VSWP
is much
different
than
zero
volts,
proceed
to
question
19.
19. Is
LVSX
Low?
If
the VSWP
voltage
is
much
different
than
zero
volts,
it
will
affect
the
PRETUNE
voltage only
if
the
AS4 YO
pretune/delay
compensation
assembly
is
also
not
operating
correctly.
If
LVSX
(low volt¬
age
sweep
disable) is high
or
intermittent, troubleshoot
the
ASS digital
interface
assembly
(in
the
controller section).
If
LVSX
is
low
(that
should be the
case
for CW/MANUAL),
the
trouble
is in
the
AS4
YO
pretune/delay
compensation
assembly.
In
either
case,
also
troubleshoot
VSWP
on
the
ASS
sweep generator
assembly.
YO UNLK
-
SWEPT MODE
To
troubleshoot
in
the
swept mode
with
the
YO
unlocked,
perform
the
following
steps:
1.
Is
CW/MANUAL
Mode Correct?
If
the
YO UNLK
error
condition
can
be
made
to
occur
in
the
CW/MANUAL
mode,
go
to
the
YO
UNLK
-
CW/MANUAL
troubleshooting
section.
It
will
also
be
helpful
if
the YO UNLK
condition
can
be
made
to
occur
in
the
SINGLE SWEEP
mode,
for
this will hold
the
YO loop (error)
condition
constant
while
troubleshooting.
If
the
error
condition
can
only
be
made
to
occur
In
the
SWEPT
mode
and
CONTINUOUS SWEEP
mode,
the
problem
will
be
more
difficult
to
solve.
Proceed
to
question
2
in
this
section.
There
are
several
malfunctions
that
could
cause
a
YO
loop
unlock
in
only
the
swept
mode
—
these relate
to
the
function and
operation
of
VSWP,
LKICK,
HLEY
(high
lock
enable
YIG
oscillator),
and possibly
VCOMP, LVSX,
and
LYSP. Most
of the
potential
causes
of the
error
are
related
to
timing,
mainly
at
the
start of
sweep.
D-18
YO
Loop
Assembly-Level
Troubleshooting
HP
8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English