Agilent Technologies 8753ES Option 011 Service Manual page 258

Source Troubleshooting
Phase Lock Error
2. If the analyzer malfunction relates to a particular frequency or range, look more closely
at the comb tooth there. Adjust the spectrum analyzer span and bandwidth as required.
Even at 3 GHz, the comb should look as clean as
instruments at 6 GHz, the comb tooth level should be approximately −46 dBm.
Figure 7-24 High Quality Comb Tooth at 3 GHz
3. If the signal at the A7 output is good, check the A7-to-A4 cable.
4. If the signal is not as clean as
assembly.
a. On the network analyzer, press
PLL AUTO OFF
SMB cable (W9) from the A7 pulse generator assembly (CW ≈ 16 MHz).
b. Set the spectrum analyzer to a center frequency of 45 MHz and a span of 30 MHz.
Connect it to the A14-to-A7 cable still attached to the A14 assembly. Narrow the
span and bandwidth to observe the signal closely.
5. If the HI OUT signal is as clean as
Otherwise, check the A14-to-A7 cable or recheck the A13/A14 fractional-N as described
ahead.
Rechecking the A13/A14 Fractional-N
Some phase lock problems may result from phase noise problems in the fractional-N loop.
To troubleshoot this unusual failure mode, do the following:
1. Set the network analyzer at 60 MHz in the FRACN TUNE mode.
2. Use a spectrum analyzer, to examine the HI OUT signal from the A14 assembly. The
signal should appear as clean as
generator to pulse generator.
7-26
Figure 7-24, observe the HI OUT input signal to the A7
System
. Otherwise do not readjust the instrument. Remove the A14-to-A7
Figure
Figure 7-25. The comb shape may vary from pulse
Figure 7-24. For Option 006
SERVICE MENU
7-25, the A7 assembly is faulty.
SERVICE MODES
Chapter 7