4-48 Service Guide E8361-90001
Troubleshooting PNA Series Microwave Network Analyzers
Measurement System Troubleshooting E8361A
Checking the A18 MA 24 Output
Perform this procedure if you observe a problem in any band and all signals from the A8
fractional-N synthesizer are present.
1. Refer to the block diagram at the back of this chapter and to “Bottom RF Cables, No
Options” on page 6-23. Locate semirigid cable W18, at the A18 MA 24.
CAUTION Be careful not to damage the center pins of the semirigid cable. Some flexing
of the cables is necessary to measure the output.
2. Using a 5/16-inch torque wrench, disconnect W18 at the A18 MA24.
3. Connect the spectrum analyzer to the open A18 connector.
4. For each frequency band in which problems were seen: Set the network analyzer to each
of the frequencies indicated in the “Network Analyzer Source Frequency Setting (GHz)”
column in Table 4-8 on page 4-47.
5. Set the spectrum analyzer to measure each of the corresponding frequencies in the
column labeled: “Expected A18 Output Frequency (GHz)” in Table 4-8 on page 4-47.
6. If the signals are <−30 dBm or not present, replace the A18 MA 24. Refer to “Removing
and Replacing the A18 MA 24” on page 7-34.
7. If the signals are present, reconnect cable W18, and then continue with “Checking the
A20 LODA Output” on page 4-48.
Checking the A20 LODA Output
Perform this test if you observe a problem in all bands on a single channel.
1. Refer to the block diagram at the back of this chapter and to “Bottom RF Cables, No
Options” on page 6-23. Locate cables W11, W12, W13, and W14, at the A20 LODA.
2. Using a 5/16-inch torque wrench, disconnect the cable associated with the faulty
channel (W11, W12, W13, or W14) and connect the spectrum analyzer to the A20 LODA
connector.
3. Set the network analyzer to any one of the frequencies listed in Table 4-8 on page 4-47.
4. Set the spectrum analyzer to measure the corresponding A18 output frequency listed in
Table 4-8.
5. If the signal is not present, replace the A20 LODA. Refer to “Removing and Replacing
the A20 LODA” on page 7-38.
6. If the signal is present, reconnect the cable, and then go to “Checking the Receiver
Group” on page 4-52.
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