HP 8340b User Manual

2.
Is
VSWP
Correct?
Check
to
see
that
VSWP
(A58TP10)
is
at
zero
volts
at
the start
of
each
sweep.
LVSX
(low
voltage
sweep
disable)
is
high in
swept
mode for
sweep
widths
>500
kHz,
but
low
in
CW/MANUAL.
Thus,
any
offset
in
VSWP
would
only
affect
the
YO tuning
in
the
SWEPT
mode.
Because
of
the
high
sensitivity
of
the
YO
frequency
to
VSWP
(500
MHz/V),
an
offset of
as
little
as
50
mV
added
from
VSWP
to
PRETUNE
will
result
in
the
YO
being
tuned
outside
of
the
capture
range
of
the
YO
phase
locked
loop.
If
VSWP
is
zero,
proceed
to
question
3.
If
VSWP
is
not
zero,
suspect
the
A58
sweep
generator.
3.
Is
the
YO
Kick
Pulse
Correct?
Make
sure
the
YO
kick
pulse
is being
generated on
the
A55
YO
driver.
a.
Check
the
LKICK signal
by
placing
the
channel
A
probe
of
an oscilloscope on
A55P1
-1.
A
TTL
low-going
signal
should
be
seen.
If
LKICK is
present,
suspect
a
failure
on
the
A55
YO
driver.
If
LKICK
is
not
present,
or does
not
drop
below
2
volts
when
active,
check
LKICK
at
A54TP2.
If
the
signal
is
good
at A54TP2,
suspect
a
motherboard
or
connector problem.
If
the
signal
at
A54TP2
is
bad,
suspect
the
A54
assembly.
4.
Is
HLEY
High
at
Start
of
Sweep?
Check
the
HLEY
(high
lock
enable
YIG
oscillator,
A50TP5)
voltage
at
the
start
of
sweep.
If
it
is
low
or
intermittent,
the
YO
loop
will
not
lock
-
suspect
the
A59
digital
interface
assembly.
HP 8340B/41B
YO
Loop
Assembly-Level
Troubleshooting
D-19/D-20

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English