112 E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Unlevels
Modulation Filter (W27). Use Table 1-18 to determine the
expected power level. If the power 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 Lowband
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. (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)
Table 1-18
Option Expected Power Level
Standard 2.3 dBm ±.5 dBm
UNW 4.5 dBm ±.6 dBm
1EH 6.5 dBm ±1 dBm
UNW+1EH 9 dBm ±1 dBm
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