HP 8340B Manual page 475

3.
Determine
the order of the spur
(i.e.
ratio of
YO frequency
change to spur frequency change).
If
the spur is
a
crossing spur, at
some point the spur
will be on top of the YO frequency and at
some
point (50
kHz away from
the YO frequency) the spur amplitude
will
decrease.
If
the
spur
is
a
crossing
spur, refer to
the appropriate spur
family
type above.
4.
To determine which internal frequency source(s)
is generating
the spur:
a.
Change the
CW
frequency
while monitoring the
SHIFT
function diagnostics, looking for
a
sudden change
in spur frequency and/or amplitude. For example, press
[SHIFT]
[M1], then
change the CW frequency. Look
for
a
correlation
between any sudden change in
spur
fre¬
quency and/or amplitude with
a change
in
M/N
output frequency or
20/30
output frequency.
If
a sudden change
in the spur occurs at the
same
time the
M/N
or
20/30 makes
a
large
change, the internal frequency source that changed
is probably one of the signals generating
the
spur.
b.
If
you
suspect the 20/30, press [SHIFT] [M3] to display the PLL2 VCO frequency
and
PLL3
up
converter frequency and
repeat
the above test.
NOTE:
For more information
on the diagnostic modes,
refer
to the Frequency Range and
CW Mode
Accuracy test in Section
IV, Performance Tests.
I/O CONNECTORS (19)
To determine source
or
destination of input or output connector signals, and for troubleshooting
information, refer to the front panel
—
rear panel functional group.
REMOTE OPERATION (20)
Section IV, Performance Tests,
contains an
HP-IB Operation
Verification Program
Listing. This
pro¬
gram
verifies
the ability of the instrument to respond
to
a
remote input (complete HP-IB handshake).
The program tests each data bit and
reads the instrument
status bytes.
If
the instrument exhibits
a
problem while
running this test, refer to the controller section functional
group.
If
you do not see
a
problem while running this
program, and the instrument does not respond properly
to other remote commands, refer to the computer documentation
to read the computer HP-IB
I/O
card
status. By outputting
the I/O card
status, the source of the
problem can be determined.
HP 8340B/41B
Assembly-Level Service Overall Instrument Troubleshooting A-49