E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Unlevels
1-69
3. If the RF signal levels are good, most likely the problem is either a detector, ALC, or modulator. Before proceeding,
turn ALC On and set the signal generator to maximum leveled power for the model and options you have and note
the frequencies where the unleveled condition occur. Later, when troubleshooting in ALC Off mode the unleveled
indication is turned off.
4. For each of the failed conditions listed, always start with the following signal generator settings:
• ALC Mode ALC Off
• Amplitude +30 dBm (max.)
• Attenuator Hold Mod On (if Option 1E1 is installed)
•RF On
• Modulation Off
Conditions:
5. Unleveled only between 250 kHz and 2 GHz. (Applies to all frequency options)
If the unleveled problem only occurs between 250 kHz and 2 GHz, the problem is most likely the
A23 Lowband Coupler/Detector.
a. Checking the A23 Lowband Coupler/Detector:
• Set the signal generator to 1.9 GHz or an unleveled signal generator frequency.
• Connect a power meter or spectrum analyzer to the A23 Lowband 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 –0.117 Vdc. Using a power meter, measure the signal level at the end of the
cable going to J3 of A30 Modulation Filter (W27). Use Table 1- 20 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.
Table 1-19 E8663D Maximum Leveled Power (dBm)
a
Frequency All Models
Std. 1EU 1E1 1E1+
1EU
100 kHz to 3.2 GHz +15 +23 +15 +23
100 kHz to 3.2 GHz w/UNX +13 +23 +15 +23
100 kHz to 3.2 GHz w/1EH
b
+13+23+15+23
100 kHz to 3.2 GHz
w/UNX + 1EH
b
+12+23+15+23
>3.2 GHz to 9 GHz +15 +23 +14 +22
a
Always check data sheet for updates to specifications
b
With Option 1EH Low-pass Filters below 2 GHz switched off. With filters on, this
specification applies above 2 GHz.
Table 1-20
Option Expected Power Level
Standard 2.3 dBm ±.5 dBm
UNW 4.5 dBm ±.6 dBm
1EH 6.5 dBm ±1 dBm
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