HP 8340b - Page 165

Verify
the
PLL2
Input
to
the
ASS
Assembly.
4.
Connect
the
oscilloscope
to A40J3.
Verify
a
CW
signal between
0.15
and
6
MHz
at
0.9V
P-P
±
0.2V.
If
this
signal
is
not
correct,
troubleshoot
the
PLL2
loop.
Further Verification
of
PLL3
5.
Use
a
frequency
synthesizer
to
inject a 150
kHz
signal
into
the
cable marked
A40J3.
6.
Connect
a
spectrum
analyzer
to A39J1.
Verify
a
160
MHz
CW
signal
at
approximately
—20
dBm.
If
this
signal
is
not
present,
repair or replace
the
A39
assembly.
7.
Change
the
frequency
synthesizer
output
frequency
to
6
MHz,
and
verify
that
the
output
of
A39J1
is a
166
MHz
CW
signal
at
approximately
—20
dBm.
If
this
signal is not
present,
repair
or
replace
the
A39
assembly.
If
the
signals
described
in
steps
6
and
7
are correct,
the
PLL3
loop
(A39
upconverter
assembly)
is
functioning
properly.
TROUBLESHOOTING
PHASE
LOCK
LOOP
1
Verifying
the Operation of the
A36
PLL1
VCO
1.
Turn
the
instruments
power
switch to STANDBY.
2.
Remove
the
A37
and
A38
assemblies
mounting
screws.
Disconnect
all
coax
cables
going
to
the
A37
and
A38
assemblies,
and
remove
the
assemblies from
the
instrument.
3.
Connect
a
spectrum
analyzer
to
A36J2.
4.
Turn
on
the
instrument's
power
switch
and
press
[INSTR
PRESET].
5.
As the
instrument
is
turned
on,
verify
a
—5
dBm
signal
at
A36J2
that
starts
at
<
200
MHz and
slowly
sweeps
up
to
a
CW
frequency
>300
MHz.
If
this
occurs,
the
VCO
is
operating,
and
is
sweeping up
to
the
high
end
of
its
tuning
range.
Do
not reinsert
the
A37
assembly,
proceed
directly
to
step
6.
If
this
does not
occur,
repair
or
replace
the
A36
PLL1
VCO
assembly.
Verifying
the
Operation
of
the
A3Q PLL1
IF
Assembly
6.
Turn
the
instrument's
power
switch
to
STANDBY.
7.
Insert
the A38
PLL1 IF
assembly
into
the
instrument and
remove
the
A36
PLL1
VCO.
8.
Connect
the
spectrum analyzer
to
A39J1.
Turn
the
instrument's
power
switch
on
and
press
[INSTR
PRESET].
Verify
that
the input
to
A38
is
a
CW
frequency
between
160.15
and
166
MHz
at
approximately
—20
dBm.
If
not,
troubleshoot PLL3.
9.
Disconnect
the
spectrum
analyzer
and
reconnect
the
coax
cable
from
the
A38
assembly
to
A39J1.
C-14
20-30
Loops
Assembly-Level Troubleshooting
HP 8340B/41B