HP 8340b User Manual

3.
Is
YO
Frequency
Within
±
25
MHz?
The
correct
YO
frequency
can
be
found
by
pressing
[SHIFT] [M2]
on
the
front
panel
that
will
display
the
following:
BAND
#
YO
FREQUENCY
(MHz)
Typically
PRETUNE
will
tune
the
YO within
±5
MHz.
YO
tune can
change
the
YO
frequency
by
±20
MHz
(capture range
of
YO
phase-locked feedback
loop).
If
the
YO
frequency
offset
is
more
than
±25
MHz,
the offset
is
more
than the
YO
TUNE
can
normally
cause
—
go
to
question
17.
If
the
YO
offset
is
less
that
25
MHz,
the
problem
is
most
likely
with
YO
TUNE
—
go
to
question
4.
4.
Is
YO
TUNE
at
Maximum
Positive
or
Negative?
(Approximately ±6.9V)
This
test
must
be
made
at
a
CW
frequency
that
exhibits the
UNLK
error
condition.
The
YO
TUNE
and
FM
COIL
cables
must
remain
connected
so
YO loop
remains
closed.
Check
the
YO
TUNE
voltage at
TP3 (TUNE)
on
the
A55
YO
driver.
When
the
loop
is
operating
properly,
the
YO
TUNE
voltage
should be
close
to
zero
volts.
If
YO
TUNE
is
within
the
range
of
approximately
±6.0
Vdc,
the
YO
loop
is
locked
and
the
UNLK
indication
is
false
—
proceed
to question
5.
If
YO
TUNE
is
at
maximum
positive
or
negative
(approximately
±6.9V),
the
YO
loop
is
unlocked
—
go
to question
6.
NOTE:
In
the CW/MANUAL
mode,
whenever
the
YO
is
locked,
YO
TUNE
should
be
within
the
range
of
±
2
Vdc.
If
the
actual magnitude
is
between
2
and
6
Vdc,
proceed
to
question
5
and
6,
and
then
return
to
question
4.
If
the
actual magnitude
of
YO
TUNE is
greater
than
approximately
6.9V,
suspect
the
A49
YO
loop phase
detector
assembly.
5.
IsHULYHigh?
If
the
YO
loop
is
actually
locked
but HULY
(high
unlock
YIG
oscillator)
is
high
indicating
unlock,
the
unlocked
detector
on
the
A49 YO
loop
phase
detector
is at
fault.
If
HULY
is
low,
the
problem
is
on
the
A59
digital
interface
assembly.
6.
IsHLEYHigh?
HLEY
(high
lock
enable
YIG
oscillator)
must
be
high
for
the
YO
loop
to
lock.
If
HLEY
is
low
or
intermittent,
suspect
the
A59
digital
interface
assembly.
If
not,
proceed
to
question
7.
7.
Is
M/N
Output
Frequency
and
Power
Correct?
Check
for
the
proper
M/N
signal
frequency
and
power
at
the
output
of
A33J2. The
correct
fre¬
quency
can
be found
by
pressing
[SHIFT]
[M1]
on
the
front
panel.
The
following
will
be displayed:
M
#
N #
M/N
FREQUENCY
(MHz)
20-30
FREQUENCY
(MHz)
The
correct
M/N
signal
power
is 0
dBm
±3
dB.
If
no
signal
is
present
or
if
the
power
and/or
frequency
is
incorrect
(at
A33J2),
troubleshoot
the
M/N
Loop.
If
the M/N
signal
is
correct,
proceed
to
question
8.
8.
Is
20-30
Output
Frequency
and
Power
Correct?
Check
for the
proper
20-30 signal
frequency
and
power
at the
output
of
A36J2.
The
correct
frequency can
be
found
by
pressing
[SHIFT]
[M1]
on
the
front
panel
(see
question
7
above).
The
correct
power
is
0
dBm
±3
dB.
If
no
power
is
present
or
if
the
power
and/or frequency
is
incorrect,
troubleshoot
the
20-30
loop.
If
the
signal
is
correct,
proceed
to
question
9.
D-16
YO
Loop Assembly-Level Troubleshooting
HP
8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English