HP 8340b User Manual

UNLOCK
ANNUNCIATOR
(6)
NOTE:
After
performing
the following
procedure,
use
the
SHIFT M4
diagnostic test
to
help
isolate
the
cause
of
an
UNLK
condition,
The
UNLK
light
indicates
that that
one or more
of
the six
instrument phase
lock
loops
is
unlocked.
1.
Press
[SHIFT]
[EXT].
OSC:
REF
M/N
HET
YO
N2
N1
appears
in
the
entry
display.
The
name
of
the
unlocked
phase
lock
loop is flashing.
The different
loops
are
listed
below,
with
information
about what
to
do
if
one
of them
is
unlocked.
REF
If
reference
loop
is flashing,
inspect
the
rear
panel,
one
of
two
conditions
should
exist:
1.
If
the
instrument
is
in
internal
10
MHz
mode:
Check
that the
INT STANDARD
BNC
and
the
EXT
STANDARD
BNC
are
connected
with
a
jumper
cable
(make
sure
the
jumper
cable
is
good).
Ensure
that the
rear
panel
REFERENCE
switch
is in
the
INT
position.
If
this is
the
case
and
REF
is
flashing,
the
instrument
requires
service.
Suspect
a
problem
in
the
reference
loop.
2.
If
the
instrument
is
in
external
10
MHz mode:
An
external
10
MHz
standard
should
be
connected
to
the
EXT STANDARD BNC
with
the
rear
panel
REFERENCE
switch
in the
EXT
position.
If
this
is
the
case
and
REF
is
flashing,
connect
the
instrument
as
described
in
step
1,
above.
Press
[SHIFT]
[EXT].
If
REF
continues
to
flash,
the
instrument
requires
service.
Suspect
a
problem
in
the
reference
loop.
If
REF
stops
flashing,
the
problem
is
caused
by
the
external
10MHz
reference standard.
If
any
of the following indicators
are
flashing,
the
instrument
requires
service:
M/N
Suspect
the M/N
loop.
HET
Suspect
a
problem
in
the
3.7
GHz oscillator
in
the
RF
section.
YO
Suspect
the
YO
loop.
N1
Suspect
a
problem
in
the
PLL1
or
PLL3
loops
in
the
20-30
loops.
N2
Suspect
a
problem
in
the
PLL2
loop
in
the
20-30
loops.
Multiple
Loops
Unlocked
The
loops
relate
to
each
other
as
follows:
•
The
REF
loop
generates
reference
signals required
by
all
other
loops.
•
The
YO
loop
uses
signals generated
by
the M/N
loop
and
the
20/30
loop.
The
UNLK
LED is
located
on
the
A2
display driver
assembly,
and
Is
driven
by
the
A3
display
pro¬
cessor,
annunciator
latch/driver.
The
LED
is
turned
on
by
the
instrument
processor.
The
processor
detects
the
unlock indication
from
the
particular phase
lock
loop,
outputs
the
appropriate
bits
on
the
data
bus,
and
outputs
address
15.-RO
to
latch
the
data
bits.
HP
8340B/41B
Assembly-Level
Service
Overall
Instrument Troubleshooting
A-39

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English