Check Fractional-N Digital (A14) With Abus - Agilent Technologies 8719ET Service Manual

Source Troubleshooting
Broadband Phase Lock Problems

Check Fractional-N Digital (A14) with ABUS

1. To setup the fractional-N tuning voltage, press the following:
PRESET: FACTORY
Preset
SWEEP TYPE MENU
Sweep Setup
System SERVICE MENU
ANALOG IN Aux Input
Meas
Format LOG MAG
21 x1 Scale Ref
Compare the fractional-N tuning voltage to
Figure 7-2 Fractional-N Tuning Voltage Waveform at Abus Node 21
2. Press
COUNTER:FRAC N
frequencies of column one in
Table 7-1 VCO Range Check Frequencies
Front Panel
50 MHz
109.999 MHz
• If the voltage waveform resembles
not match Table
7-14
Preset
LOG FREQ
ANALOG BUS ON
COUNTER: ANALOG BUS
AUTO SCALE
Sweep Setup
Table 7-1.
Displayed Counter Value
119.988 to 120.012 MHz
239.975 to 240.024 MHz
Figure 7-2 on page
7-1, A14 is the most probable fault.
Figure 7-2.
and set the instrument to the
CW FREQ
7-14, but the counter values do
8719ET/20ET/22ET
8719ES/20ES/22ES
RF Network Analyzers
Service Guide