Troubleshooting Performance Tests

If any performance test should fail, you should:

Verify that your test connections are correct.
Ensure the equipment connections are torqued to proper specs.
Check cables and adapters for damage.
Check the input and output connectors on the test equipment for damage.

For tests that have external test equipment locked to the 10 MHz reference out of the M9300A frequency reference module, there is a potential for the Connection Checking to state that the ETE unexpectedly senses or unexpectedly does not sense a 10 MHz reference input. If this occurs, you can either Ignore and Continue past the prompt, or use a different M9300A reference module or ETE signal generator/spectrum analyzer.

The table below shows troubleshooting specific to the performance tests listed.

Performance Test	Troubleshooting Information
Internal Alignment	This is run within the downconverter and includes an LO Nulling, IF alignment, and Amplitude Alignment – in that order. If this fails or reports an error, the most likely cause is a bad downconverter module. The Self Test that is run before and after the alignment should catch this error and report the responsible module. If there is a module failure, it is very likely that Self-Test will catch the issue. If this fails, it could mean a number of things. Read the errors reported from Self-Test (usually the first 5 lines show the origin of the problem) and verify that it is not improperly connected cables or incompatible firmware versions. If the reported errors state internal hardware failures or measurements out of limits, then the reported module will need servicing.
LO Nulling	This is run in the first mixer of the downconverter in the frequency range of 100 MHz to 400 MHz. If this test exceeds its maximum power limit (-10 dBm), the most likely problem is a broken downconverter module. See the service guide for manual tests on how to check for a failing downconverter module.
Displayed Average Noise Level	The best process to troubleshoot a Displayed Average Noise Level (DANL) failure is to look at the test results in the generated N7872A VSA test report. Look at each path and setting (for example, Pre-Amp ON/OFF). If only one path fails and the rest pass, then the issue probably resides in the downconverter. If all paths fail, then the issue could reside in the digitizer or possibly the synthesizer modules. See the service guide for manual tests to test each module.
IF Flatness	If this test fails, then either the digitizer or downconverter module is defective. See the service guide for manual tests to check each module.
IF Bandwidth Filter Switching Uncertainty	A downconverter failure is the most likely cause for this test to fail. See the manual tests in the service guide, and make sure to pay special attention to the 15 MHz and 160 MHz IF signals
Expected Input Level Switching Uncertainty	A downconverter failure is the most likely cause for this test to fail. Check the N7872A VSA test reports to see if there is any indication of where the failure resides. If you can determine that a certain setting (for example Pre-Amp ON) is consistently failing, then the Pre-Amp in the downconverter is defective. See the service guide for manual tests.
Absolute Amplitude Accuracy	If this test fails, the best way to find the module causing the failure is to analyze the N7872A VSA test report. Look for consistent failures of a single path or setting, and if there is only one or two paths that fail, this indicates that the downconverter is defective. If all the paths fail, then the digitizer could be defective. If you notice a power spike or power dips, then the synthesizer probably failed and is not providing the required power or frequency to the downconverter mixers. See the service guide for manual tests for each module to find the defective module. For the M9391 VSA, if the module temperature is out of the controlled temperature range (module temperature 40–51 °C) and a test point fails, then that test point will be reported as invalid and the entire test run will be flagged as invalid. To lower the module temperature to the controlled temperature range, set the chassis fan switch to High and verify that all unoccupied slots have slot blockers installed.
Third Order Intermodulation Distortion	Improper test setup is likely the cause for this test to fail. The most common mistake is to install the directional bridge backwards. If everything is properly connected, analyze the test report. There are 2 settings (pre-amp ON or pre-amp OFF) and if only one passes or only one fails, then most likely the Pre-Amp in the downconverter is defective. Also, if all of the previous tests passed and this test failed, then it could be caused by a digitizer failure. See the service guide for more troubleshooting tips.
Amplitude Linearity	If this test fails, then either the digitizer or downconverter module is defective. See the service guide for manual tests to check each module.