Isolate The Fault In The Rf Path - Agilent Technologies 8719ET Service Manual

8719ET/20ET/22ET
8719ES/20ES/22ES
RF Network Analyzers
On ET models, if directivity looks bad, substitute a known good load to the
REFLECTION port. If the directivity is still bad, troubleshoot the REFLECTION
port. If the directivity is good, the load is bad.
• Shorts and opens: If the source match and reflection tracking terms look good, the
shorts and the opens are good. If these terms look bad while the rest of the terms
look good, proceed to

Isolate the Fault in the RF Path

Since the calibration devices have been verified, the problem exists in the test port
connector, the coupler, or elsewhere in the internal RF path.
assemblies affect each error term. If more than one error term is bad, note which
assemblies are common to each of the bad terms. These are the suspects.
The method of fault isolation that must be used is assembly substitution.
Assembly Substitution Fault Isolation
IMPORTANT Before trying this, be sure to inspect the front-panel test-port connector for
obvious damage. Tighten all semi-rigid cable connectors inside the
instrument with a calibrated torque wrench.
At this point, the error term problem has been isolated to a specific port and you should
have a list of suspected assemblies.
1. On ES models, swap identical assemblies between the PORT 1 and PORT 2 signal paths
and then regenerate the error terms.
NOTE On ET models where a duplicate assembly is not present, the analyzer will
have to be sent in to your local Agilent Technologies service center. Refer to
Chapter 13 , "Replaceable Parts,"
2. If the problem moves from one port to another, you have found the offending assembly.
Service Guide
"Verify Shorts and Opens by Substitution" on page
for instructions for returning an analyzer.
Accessories Troubleshooting
Inspect the Error Terms
9-7.
Table 9-1 shows which
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