Agilent Technologies PSG Series Service Manual page 64

4. For each of the failed conditions listed, always start with the signal generator set to the following settings.
• ALC Mode ALC Off
• Amplitude +30 dBm
• Attenuator Hold Mod On
• RF On
• Modulation Off
Conditions:
5. Unleveled only between 250 kHz and 2 GHz.
If the unleveled problem only occurs between 250 kHz and 2 GHz, the problem is most likely the
A23 Low Band Coupler/Detector.
a. Checking the A23 Low Band Coupler/Detector:
• Set the signal generator to 1.9 GHz or a frequency where the signal generator is unleveled.
• Connect a power meter or spectrum analyzer to the A23 Low Band Coupler/Detector output.
• Set the signal generator to 1 GHz. Using the RPG adjust the amplitude level so the detected voltage
on cable J5 of A10 ALC (W14) is -.117 Vdc. Using a power meter, measure the signal level at the end
of the cable going to J3 of A30 Modulation Filter (W27). The power level should read 2.3 dBm .5
dB. If the voltage can not be adjusted to this level, troubleshoot the RF path.
• If the problem is at some frequency other than 1 GHz, repeat the above step using the problem
frequency. The dB p-p variation from 250 kHz to 2 GHz should be <2 dB.
• If the dc level is bad, replace the A23 Low Band Coupler/Detector.
• If the signal is good, replace the A10 ALC.
6. Unleveled only between 250 kHz and 3.2 GHz. If the unleveled problem only occurs between 250 kHz and
3.2 GHz, the problem is most likely the A8 Output or A10 ALC.
a. Checking Lowband Modulator Drive signal.
• Set the signal generator to a frequency between 250 kHz and 3.2 GHz. Set the amplitude so the
power meter reads +21 dBm on cable W27 going to J3 on A30 Modulation Filter.
• Measure the voltage on the center pin on A31 Motherboard connector J1122. The voltage should be
around +2.0 Vdc.
• Reduce the amplitude setting to 0 dBm and the voltage on J1122 should move towards +.15 Vdc.
• If the voltages are not correct or do not change as power is changed, replace the A10 ALC.
• If the voltage changes, replace the A8 Output.
7. Unleveled only between 2 GHz and 20 GHz or 40 GHz. If the unleveled condition occurs only for
frequencies >2 GHz to 20 GHz or 40 GHz, the problem is most likely the A25 Highband Coupler/Detector.
a. Checking the A25 Highband Coupler/Detector
• Set the signal generator frequency to 19 GHz or a frequency where the signal generator is
unleveled.
• Connect a power meter or spectrum analyzer to the RF output connector.
• Using the RPG adjust the power until the measured power level is +9 dBm. If the power can not be
Troubleshooting
Troubleshooting Unlevels
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