E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Unlevels
1-70
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. (Applies to all frequency options)
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 (or the maximum settable power) on cable W27 going to J3 on A30 Modulation Filter.
If the power can not be set and options 1EH and/or UNW are installed, use the RF path block diagram to
verify the power levels through each device.
• 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 +0.15 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 the maximum frequency. If the unleveled condition occurs only for frequencies
>2 GHz to the maximum frequency, the problem is most likely the A25 Highband Coupler/Detector. (Applies to all
frequency options)
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- 21 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.
UNW+1EH 9 dBm ±1 dBm
Table 1-21
Power
Level
Expected Voltage Level
at J3 Center Pin
+9 dBm –30 mVdc ±10Vdc
+7 dBm –20 mVdc ±10Vdc
+3 dBm –10 mVdc ±10Vdc
Table 1-20
Option Expected Power Level
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