E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Assembly–Level Problems
1-49
Power: +20 dBm
Pulse Modulation: On
Period: 40s
Pulse Width: 10 ns
RF: On
3. The voltage measured by the DVM should be approximately 0V. If it is not, use an oscilloscope to view P131–6 of
the A31 Motherboard (this is the pulse signal out of the A11 Pulse/Analog Modulation Generator).
Change the pulse period to 1 ms and the pulse width to 500 μs.
• If the pulse is not present, perform the A11 Pulse/Analog Modulation Generator self–test, and follow the
troubleshooting procedure.
4. If pulse modulation is working, perform the A8 Output self–test.
• If the self–test passes, refer to “Troubleshooting the RF Path” on page 1- 75, and check the lowband path.
• If the self–test fails, refer to the A8 Output test troubleshooting.
Lowband Pulse Off
1. Disconnect the cable from J5 of A10 ALC, and connect the cable to a DVM (this is the lowband detector output).
2. On the signal generator, set the following:
Center Frequency: 3 GHz
Power: +20 dBm
Pulse Modulation: On
Period: 40s
Pulse Width: 39.9s
RF: On
3. The voltage measured by the DVM should be approximately −2.2 V. If it is not, use an oscilloscope to view P131–6
of the A31 Motherboard (this is the pulse signal out of the A11 Pulse/Analog Modulation Generator).
Change the pulse period to 1 ms and the pulse width to 500 μs.
• If the pulse is not present, perform the A11 Pulse/Analog Modulation Generator self–test, and follow the
troubleshooting procedure.
4. If pulse modulation is working, perform the A8 Output self–test.
• If the self–test passes, refer to “Troubleshooting the RF Path” on page 1- 75, and check the lowband (<3.2 GHz)
path.
• If the self–test fails, refer to the A8 Output test troubleshooting.
1208 Quadraplier
1. If the power supplies +15V, −15V, −3V, −5.2V, +6.5V, +3.5V, or −3V fail, refer to the table on page 1- 47, and check
the supplies used by the A35 I/Q Modulator as they leave A26 MID connector.
If the signals are good at the A26 MID connector, replace the A36 Quadraplier.
2. If the TC902, TC956 or any of the drain currents fail (test indexes 6 through 24), replace the A36 Quadraplier.
3. If self–test 20–40 GHz Prelevel, index 25, fails:
a. On the signal generator, set the following:
Center Frequency: 30 GHz
Power: −20 dBm
RF: On
b. Remove the cable from J6 of the Quadraplier Bias Board and connect it to a DVM.
c. The signal should measure approximately +5.2 Vdc.
1. If the signal is bad, troubleshoot the RF path.
2. If the signal is good, replace the A36 Quadraplier.
4. If self–test 20–40 GHz Prelevel, index 26, fails:
a. On the signal generator, set the following:
Center Frequency: 45GHz
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