HP 8340b User Manual

M/N
OUTPUT
FREQUENCY INCORRECT
NOTE:
Before replacing
A31,
A32, or
ASS,
remove
the
assembly
from
the
instrument
and verify
that
the
appropriate
power
supply
voltages
are
present
at the
assembly's
input.
Refer
to the
end
of
the
Service
Introduction
in
this
manual
power
supply
input
information.
For
the
A31
and
ASS
assemblies,
a
missing
power
supply
will
be
caused
either
by
a
failure
on
the
A34
reference
loop
—
M/N
loop
motherboard
or
a
failure
in
the
power
supplies.
In
the
case
of
A32,
a
missing
power
supply
could
also
be
due
to
a
failure
on
A33.
1.
ON
the
DUT,
press
[INSTR
PRESET]
[CW].
Either
set
the
DUT
to
a
CW
frequency
that
causes
and
incorrect
M/N
Loop output frequency
(M/N
OUT),
or
to
a
CW
frequency
that
causes
the
front
panel
UNLK
annunciator
to
light.
2.
Press
[SHIFT]
[EXT].
The following
phase
lock
loop
diagnostic
should
be
displayed
in
the
ENTRY
DISPLAY:
OSC: REF
M/N
HET
YO N2
N1
If
REF
is
flashing,
troubleshoot
the
reference
loop.
The
reference
loop must
be
phase-locked
before
the
M/N
loop
can
phase-lock.
3.
Connect
the
frequency
counter's
FREQ STD
OUT
to
the
DUT's
rear
panel
EXT FREQUENCY
STANDARD
input.
Switch
the
DUT's
FREQUENCY STANDARD
switch to
the
EXT
position
(the
EXT REF
annunciator
should
be
on).
4.
Verify
that
the
output
frequency
from
A29J2
is
20
MHz
±2
Hz
and
that
its
output
power
is
0
dBm
±3 dB.
If
the
signal's
frequency
or
power
level
is
incorrect,
troubleshoot
the
reference
loop.
5.
Verify
that
the
output
frequency
from
A30W1
is
400
MHz
±2
Hz
and
that
its
output
power
is
approximately
—10
dBm
±3dB.
If
the
signal's
frequency
or
power
Is
incorrect
troubleshoot
the
reference
loop.
6.
On
the
DUT,
press
[SHIFT]
[M1].
The
DUT
will
display,
from
left
to
right,
the
following
information:
M
Divide
N
Divide
M/N
OUTput
20/30
OUTput
Number
Number
Frequency
(MHz)
Frequency
(MHz)
Verify that
the
signal
out
of
A33J2
is
at
the
displayed
M/N
output
frequency ±2
Hz
and
that
its
power
level
is
3
dBm
±3 dB.
If
the
output
frequency
is
incorrect,
proceed
to
step
7.
If
the
output
frequency
is
correct
but the
output
power
is
low,
perform
the M/N Divider Verification
and
Low
Output
Power
Troubleshooting
above.
7.
Remove
the
SMB
cable,
A31W2, from
A33J1
and
install
an
SMB
tee
onto
A31W2. Connect
the
second port
of the
tee
to
A33J1
(you
will
need to
use
an
SMB
Jumper
cable)
and
connect
the
third
port
to
the
frequency
counter's
10
Hz
—
500
MHz
input.
8.
Multiply
the
displayed
M/N
output
frequency
by
two
and
verify
that
the
counter
indicates
this
frequency
±2
Hz.
If
the
output
frequency
is
correct,
replace
A33.
If
the
frequency
is
incorrect,
proceed to
step
9.
9.
Switch
the
DUT
to STANDBY.
Remove
the
A31
assembly
from
the
instrument and place
it
on
an
extender
board.
Switch
the
DUT
ON.
The
M
and
N
divide
numbers
should
still
be
displayed
in
the
POWER
dBm
display.
HP
8340B/41B
M/N Loop
Assembly-Level
Troubleshooting B-23

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English