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86 E8257D/67D, E8663D PSG Signal Generators Service Guide

Troubleshooting

Troubleshooting Assembly–Level Problems

— If the dc voltage is approximately –2.2 Vdc, replace the A10 ALC.

7. If other dc voltages are present, check for dc voltage on the output of the

lowband detector.

— If a dc voltage is present, replace the cable.

— If no dc voltage is present, replace the lowband detector.

1205 LB Pulse Mod

Lowband Pulse On

1. Disconnect the cable from J5 of the 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: 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 122, and check the lowband path.

— If the self–test fails, refer to the A8 Output test troubleshooting.

Lowband Pulse Off