Keysight CXG, EXG, and MXG X-Series Signal Generators Service Guide 135
Troubleshooting
Unleveled Issues
Since the hardware within the ALC loop differs by instrument model, follow the
troubleshooting procedure below for the instrument being serviced.
N5171B, N5181B
These instruments do not have any other assembly inside the ALC loop other
than the A3 RF assembly. So, the ALC detectors, the ALC control, and the ALC
modulators are all located on the A3 RF assembly. Any unlevel condition
encountered is either the result of a hardware issue on the A3 RF assembly or
of an adjustment error. To isolate the cause of the unlevel perform the
following steps:
1. Verify the power supply voltages by seeing the “Power Supply Status
Quick-Check” section in Chapter 8, “Power Supply”.
2. Verify that the instrument is using the factory calibration data by restoring
the data. See “Calibration Data Restore” in Chapter 3, “Instrument
Information and Calibration Data”.
3. Run the following adjustments:
ALC Linearity Calibration
Absolute Power Calibration
ALC Calibration
4. If the adjustments fail or the unlevel condition persists, replace the A3 RF
assembly.
N5166B, N5172B, N5182B
Since the main difference between these models and the others is the addition
of the A2 Vector BBG assembly, first determine if the A2 Vector BBG assembly
is the cause of the unlevel. Use the following procedure to do so:
1. If the instrument has option 012 verify that the rear panel LO jumper cable
(W16) is connected between the LO OUT and LO IN ports.
2. Determine if the unlevel error only occurs when the I/Q modulator is
turned on.
— If the unlevel error occurs only when the I/Q modulator is turned On
go to the “I/Q Modulator Unlevel” section to continue
troubleshooting this error.
3. Verify the power supply voltages by seeing the “Power Supply Status
Quick-Check” section in Chapter 8, “Power Supply”.
4. Verify that the instrument is using the factory calibration data by restoring
the data. See “Calibration Data Restore” in Chapter 3, “Instrument
Information and Calibration Data”.
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