Keysight Technologies E8257D Service Manual page 86

Troubleshooting
Troubleshooting Assembly–Level Problems
7. If other dc voltages are present, check for dc voltage on the output of the
1205 LB Pulse Mod
Lowband Pulse On
1. Disconnect the cable from J5 of the A10 ALC, and connect the cable to a
2. On the signal generator, set the following:
3. The voltage measured by the DVM should be approximately 0V. If it is not,
4. If pulse modulation is working, perform the A8 Output self–test.
Lowband Pulse Off
1. Disconnect the cable from J5 of the A10 ALC, and connect the cable to a
2. On the signal generator, set the following:
86
— If the dc voltage is approximately –2.2 Vdc, replace the A10 ALC.
lowband detector.
— If a dc voltage is present, replace the cable.
— If no dc voltage is present, replace the lowband detector.
DVM (this is the lowband detector output).
Center Frequency: 3 GHz
Power: +20 dBm
Pulse Modulation: On
Period: 40s
Pulse Wid th: 10 ns
RF: On
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.
— If the self–test passes, refer to
page 122, and check the lowband path.
— If the self–test fails, refer to the A8 Output test troubleshooting.
DVM (this is the lowband detector output).
Center Frequency: 3 GHz
Power: +20 dBm
Pulse Modulation: On
Period: 40s
Pulse Wid th: 39.9s
RF: On
E8257D/67D, E8663D PSG Signal Generators Service Guide
"Troubleshooting the RF Path" on