First LO Span Problems (All Spans)

1. Set the HP 8560A to the following settings:

C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz

SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lMHz

RES BW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lMHz

VIDEO BW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lMHz

SWEEPTIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50ms

2.Check that there is 0 V to +lO V ramp of 50 ms duration at A14Jl5 pin 15.

3.If a scan ramp is not present, refer to “Sweep Generator” in this chapter.

4.If there is a 0 to -10 V ramp at A14J15 pin 14, the fault is probably in the Main/FM/VCO S weep Switch. See function block G of Al4 Frequency Control Schematic (sheet 2 of 5).

5.Check that there is a 0 V to +lO V ramp at U325 pin 1. The analyzer’s ADC obtains information about the sweep from this node.

6.Continue with step 7 to check the Span Attenuator. See Function Block M of Al4 Frequency Control Schematic (sheet 2 of 5).

7.With the analyzer set to the settings in step 1, monitor A14U323 pin 6 with an oscilloscope. A 0 V to -10 V ramp should be present.

8.Change the HP 8560A’s span to 500 kHz and check for a 0 V to -5 V ramp at U323 pin

6.

9.Change the HP 8560A’s span to 200 kHz and check for a 0 V to -2 V ramp at U323 pin

6.

10.Set the HP 8560A to the following settings:

START FREQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..l0 MHz

STOP FREQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 GHz

SWEEPTIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80ms

11.Monitor A14J15 pin 14 for a 0 V to -9 V ramp. Switches U317A, U317B, and U317D should be open and U317C should be closed.

12.Change the HP 8560A’s SPAN to 365 MHz and check for a 0 mv to -900 mV ramp at A14J15 pin 14. Switch U317C should be open and U317B closed.

13.Change the HP 8560A’s SPAN to 36.5 MHz and check for a 0 mV to -90 mV ramp at A14J15 pin 14. Switch U317B should be open and U317A closed.

14.Check the Sweep Generator’s Current Source with the following steps (function block K of Al4 Frequency Control Schematic).

15.Set the HP 8560A to the following settings:

C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz

SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lMHz

SWEEPTIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50ms

16.Use a DVM to monitor the voltage at A14J18 pin 4. The voltage should measure approximately -8.45 Vdc.

Synthesizer Section lo-21