Agilent Technologies 85032B/E 50 Specifiche Pagina 172

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Troubleshooting and Block Diagrams 8712ET/ES and 8714ET/ES
Category 2 Failures: No Error Messages but One or More Measurements Are Nonfunctional RF Network Analyzers
4-30 Service Guide
General Troubleshooting for Both ET and ES Models
This section describes further troubleshooting practices for both the ET and ES analyzers.
The focus of this section is a more detailed look at the fractional-N/referecnce board
assembly (A3), the source board assembly (A4) and the ADC check for the receiver board
assembly (A5).
Troubleshooting the Fractional-N/ Reference Board (A3)
Verifying the 10 MHz reference signal
Perform these steps.
1. Remove the handles and front panel (refer to “Removing the Front Panel Assembly” on
page 3-4).
2. Connect an oscilloscope or a frequency counter to A3J2 (the connector on the right) to
measure the 10 MHz output from the A3 fractional-N/reference board (refer to
“Removing the Fractional-N/Reference Assembly” on page 3-10).
NOTE The output signal must be measured with a 50 load attached to the
RF OUT/PORT1 port. Typically this signal consists of a 2 V, 15 ns pulse into
50. The frequency should be 10 MHz ± 50 Hz (see Chapter 2, “Adjustments”
to adjust the frequency of the internal reference).
If the signal is not 10 MHz, verify that the external reference has not been selected by
pressing and making sure that is displayed. If it is still not
correct, replace the fractional-N/reference board (refer to “Removing the
Fractional-N/Reference Assembly” on page 3-10).
Measuring the Sweep Output Fractional-N/Reference Assembly
1. Set the analyzer in the CW and trigger hold modes and step through the frequencies in
Table 4-2. Check the fractional-N output at A3J301 (the connector on the left). It is
recommended that you use a spectrum analyzer’s 10 MHz reference signal as the
10 MHz external reference for the network analyzer.
The typical amplitude of this signal should be in the 0 to +4 dBm range. Any harmonics
should be less than 16 dBc.
Table 4-2 Source Frequency Versus Fractional-N Frequency
8712ET/ES 8714ET/ES
Source
Frequency
Fractional-N
Frequency
Source
Frequency
Fractional-N
Frequency
300 kHz 36.567187 MHz 300 kHz 31.993251 MHz
500 MHz 44.375 MHz 500 MHz 38.825087 MHz
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