Agilent Technologies 8590 Series Service Manual page 236

Troubleshooting the Analyzer
Isolating an RF, LO, IF, or Video Problem
If the displayed signal is distorted
This failure may result in the displayed signal having distinct lobes on
each side. A high noise floor may also be present.
Note that an intermittent hardware failure during the
self-calibration routine can cause this type of amplitude failure. The
erroneous calibration data causes the failure symptoms even while the
hardware is operating normally.
1. If the signal looks normal when
values in the RFATN and SGAIN columns using
as described in "Using the Internal Service-Diagnostic Routines."
If a correction factor in either column is greater than two, there may
be a failure on the input attenuator or the A12 amplitude control
assembly.
Refer to Chapter 13
disabled when
CORRECT ON OFF
2. Troubleshoot the input attenuator or step gain symptoms with
CORRECT ON OFF
3. Measure the 321.4 MHz input to the A9 third converter assembly by
connecting the CAL OUT to the INPUT 50Ω with a BNC cable.
75 Ω input only: Connect the CAL OUT to the INPUT 75Ω with the
75 Ω BNC cable.
Then, disconnect the W9 cable assembly from the third converter
and measure at the cable output.
The 321.4 MHz input typically measures between −36 and −39 dBm
with zero input attenuation.
4. Check the signal path from the analyzer input to the output of the
A14 log amplifier assembly. Refer to
located in Chapter 5
Recalibration of the analyzer is necessary after the adjustment or
replacement of each suspect assembly. A functioning analyzer may still
appear to be defective if calibration data from before the repair is used.
If the signal is off frequency
This failure may result in the
Perform all of the internal service-diagnostic routines.
Refer to "Using the Internal Service-Diagnostic Routines"
chapter.
236
CORRECT ON OFF
for the description of the corrections that are
is off.
turned off.
"IF Power-Level Measurement"
of this service guide.
self-calibration routine failing.
CAL FREQ
CAL AMPTD
is off, check the
DISPLAY CAL DATA
in this
Chapter 4