Agilent N5161A/62A/81A/82A/83A MXG Signal Generators Service Guide
Troubleshooting
No GPIB Activity
1-65
No GPIB Activity
The signal generator supports a general purpose interface bus (GPIB). The GPIB enables communication with compatible devices such as
external controllers.
1.
Replace the GPIB cable with a known working cable.
2.
Send a SCPI command to the signal generator.
3.
Verify the signal generator responds to the SCPI command.
4.
If the signal generator does not respond to the SCPI command, replace the A5 CPU assembly.
Error Messages
For more information on Error Messages go to the error messages list on the documentation CD, N5180-90007, or online at
http://cp.literature.agilent.com/litweb/pdf/N5180-90020.pdf.
Troubleshooting Unlocks
The phase lock loop refers to the frequency generating circuit used to maintain the phase relationship between the frequency generation loop
and a reference frequency. By maintaining the phase relationship, the frequency accuracy of the signal generator is guaranteed.
To maintain accuracy, the phase lock loop compares the phase of a signal from the reference assembly to the phase of the frequency loop
signal. If the two signals are out of phase, the phase comparator circuit adjusts the frequency loop signal until the signals are in phase. If the
phase comparator circuit cannot adjust the phase of the frequency loop signal, the phase comparator rails and generates an unlocked
message. The unlock message will be displayed on the front panel.
Troubleshoot multiple loop unlock messages in the following order:
1.
“508 Frac-N Loop Unlock” on page 1-65
2.
“512 Reference Unlocked” on page 1-65
3.
“515 Reference Missing” on page 1-66
4.
“532 PCI Bridge FPGA DCM Unlocked” on page 1-66
5.
“533 RF Analog FPGA DCM Unlocked” on page 1-66
508 Frac-N Loop Unlock
A 508 Frac-N Loop Unlock message indicates a problem with the Voltage Control Oscillator's (VCO)
phase-locked loop on the A3 RF assembly.
•
If the signal generator is connected to an external reference:
1.
Check the reference’s frequency, power, and physical connection.
2.
Make sure the external reference frequency, specified in the instrument setup, is correct.
3.
If the external reference signal and connection is good, replace the A3 RF Assembly.
•
If the signal generator is not connected to an external reference:
1.
Replace the A3 RF assembly.
2.
Chapter 4, "Post-Repair Procedures and Performance Verification"
512 Reference Unlocked
A 512 Reference Unlocked message indicates a problem with the external reference settings or connections.
•
If the signal generator is connected to an external reference:
1.
Check the reference’s frequency, power, and physical connection.
2.
Make sure the external reference frequency, specified in the instrument setup, is correct.
3.
If the external reference signal and connection is good, replace the A3 RF Assembly.
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