E8257D/67D, E8663D PSG Signal Generators Service Guide 113
Troubleshooting
Troubleshooting Unlevels
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 to the highest level possible.
This level will be either +9 dBm, +7 dBm, or +3 dBm,
depending on the mix of installed options. If the power can
not be adjusted to one of these levels, troubleshoot the RF
path.
— Remove the cable from J3 on the A10 ALC and measure the
dc voltage on the center pin of the cable. Use Table 1-19 to
determine the expected power level.
— Set the power level to 0 dBm and repeat the center pin
measurement. The voltage should be –5 mVdc ±10 mVdc.
— If the voltages are good, go to step 8.
— If the voltages are the same, replace the A25 Highband
Coupler/Detector.
8. Unleveled only between 3.2 GHz and 20 GHz. (Applies to all frequency
options)
If the unleveled condition occurs between 3.2 GHz and 20 GHz, the
problem is most likely the A30 Modulation Filter.
a. Checking the A30 Modulation Filter:
— Set the signal generator to 20 GHz or a frequency where the
signal generator is unleveled and measured RF output level is
+7 dBm or +3 dBm, depending on options. If the power can
not be set to +7 dBm or +3 dBm, troubleshoot the RF path.
— Remove the cable going to J6 on the A30 Modulation Filter
and measure the voltage on the center pin. The voltage
should be approximately +5.4 Vdc.
— Set the amplitude to –15 dBm. The voltage on the center pin
should decrease a few mVdc.
— If the voltages are good, replace the A30 Modulation Filter.
Table 1-19
Power Level Expected Voltage Level at J3 Center Pin
+9 dBm –30 mVdc ±10Vdc
+7 dBm –20 mVdc ±10Vdc
+3 dBm –10 mVdc ±10Vdc
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