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Troubleshooting
Troubleshooting Assembly–Level Problems
401 Prelevel Loop Test
1. With the signal generator powered up, carefully remove the A8 Output.
2. Set the signal generator to 3 GHz CW.
3. Using a spectrum analyzer measure the A6 Frac–N RF output at J4 of the A8 Output.
The signal at J4 should be at 3 GHz and ≥0 dBm.
• If the signal is not present, or is not at the correct level, replace the Frac–N.
• If the signal is present, replace the A8 Output.
WARNING Do not re–install the A8 Output with the signal generator turned on, or
serious damage to the signal generator can result.
402 Quadrature DAC Test
• Replace the A8 Output.
403 VBLO Test
• Replace the A8 Output.
404 Marble Test
1. Measure the Q signal from the A13 I/Q Multiplexer:
a. Disconnect the cable from J1052 A31 Motherboard and connect it to a DVM.
b. Set the CW frequency to 2 GHz.
c. Turn on the I/Q modulation, and make the Q offset the active function:
1. Press the
I/Q hardkey.
2. Select
I/Q On > I/Q Adjustments > I/Q Adjustments On > Q Offset
d. As you rotate the RPG, the voltage displayed on the DVM should vary from approximately
+0.25 Vdc for an offset of 50%, to approximately −0.25 Vdc for an offset of −50%.
If the signal is bad, check it at J10 of the A13 I/Q Multiplexer.
• If the signal is bad at J10, refer to the A13 I/Q Multiplexer troubleshooting, on page 1-30.
• If the signal is good at J10, change the cable.
2. Measure the I signal from the A13 I/Q Multiplexer:
a. Reconnect the cable removed in Step 1.
b. Disconnect the cable from J1053 A31 Motherboard and connect it to the DVM.
c. Leave the I/Q modulation on, and make the I offset the active function.
d. As you rotate the RPG, the voltage displayed on the DVM should vary from approximately
+0.25 Vdc for an offset of 50%, to approximately −0.25 Vdc for an offset of −50%.
If the signal is bad, check it at J9 of the A13 I/Q Multiplexer.
• If the signal is bad at J9, refer to the A13 I/Q Multiplexer troubleshooting, on page 1-30.
• If the signal is good at J9, change the cable.
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