HP 8340B Manual 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