Agilent Technologies 856290216 service manual Troubleshooting the Cal Oscillator with the TAM

3. Set the other spectrum analyzer controls as follows:
Span	. ..5MHz
Reference level	- 2 0 dBm
Center frequency	..10.7MH z

4.On the HP 85623 spectrum analyzer, set the cal oscillator to 10.7 MHz by selecting Fixed Tuned to 10.7 MHz .

5.A -25 dBm signal from A5J5 should be displayed. If the signal is missing, disconnect W52 (coax 9) from A5J4. This is the cal oscillator signal input from the cal oscillator on the A4 assembly.

6.Connect the end of cable W52 to the input of the second spectrum analyzer. The signal coming from cable W52 should be -35 dBm at 10.7 MHz. If the cal oscillator signal from cable W52 is correct, the A5 IF assembly is probably at fault.

Troubleshooting the Cal Oscillator with the TAM

1.Enter the TAM Cal Osc Troubleshooting Mode.

2.On the HP 85623 spectrum analyzer, disconnect cable W52 (coax 9) from A5J4 and connect this end of cable W52 to the input of a second spectrum analyzer.

3.Set the controls of the second spectrum analyzer connected to cable W52 to the following:

Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5MHz Reference level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -30 dBm Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 MHz

4.Select each of the fixed-tuned frequencies. Verify at each frequency that the signal amplitude measures -35 dBm. If the frequency is incorrect, do the following:

a.Verify that the reference divider output (A4U811 pin 9) is 100 kHz. If it is not, verify that the 10 MHz reference is present at A4U811 pin 1.

b. Verify that the frequency found on the output of the divider (A4U808 pin 15) matches the output of the reference divider. Matching frequencies indicate the oscillator loop is locked. If the loop is not locked, troubleshoot the divider, oscillator, or phase detector.

c.Verify that the frequency found at the divider input (A4U808 pin 3) matches the CW frequency chosen in step a. Matching frequencies indicate a properly working oscillator. If the frequency is different, troubleshoot the divider.

d. Repeat step c for all the CW frequencies provided by the test.

5.Select each of the sweep widths (these sweeps are centered about 10.7 MHz).

6.Reduce the span of the other spectrum analyzer to check that the cal oscillator is actually sweeping. If the oscillator is not sweeping, perform the following steps:

a. The output of the sweep generator circuit (A4U804 pin 8 of function block Z) should be a series of negative-going parabolas (frequency and amplitude vary depending on the sweep width chosen). Table 9-3 lists the RANGE, MAO, and MA1 values for the sweep widths. If a failure is indicated in the IF/LOG CHECK, press More Info to provide more detailed information about the detected failure. If an HP-IB printer is available, connect it to the HP 85623 spectrum analyzer HP-IB connector, then press Print Page for a hard-copy output.

9-8 IF Section