E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Assembly–Level Problems
1-35
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- 29.
• 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- 29.
• If the signal is good at J9, change the cable.
3. If both the I and Q signals are good, reconnect the cable removed in Step 2 Check the signals at the A8 Output
board.
a. At J53–8, repeat the Q offset check in Step 1
• If the signal is good, replace the A8 Output board.
• If the signal is bad, replace the A31 Motherboard.
b. At J53–19, repeat the I offset check in Step 2
• If the signal is good, replace the A8 Output board.
• If the signal is bad, replace the A31 Motherboard.
405 Gain Adjustment Test
• Replace the A8 Output.
406 Prelevel Bypass Test
• Replace the A8 Output.
407 Switched Filters Test
• Replace the A8 Output.
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