Agilent Technologies 8753ES Option 011 Service Manual page 252

Source Troubleshooting
Phase Lock Error
A13/A14 Fractional-N Check
Use the analog bus or an oscilloscope to check the A14 VCO's ability to sweep from 30 MHz
to 60 MHz. The faster analog bus method should suffice unless problems are detected.
Fractional-N Check with Analog Bus
1. Press
Preset System
S PARAMETERS
the fractional-N counter.
2. Press
Sweep Setup
3. Set the instrument as indicated in
frequencies listed.
Table 7-5 VCO Range Check Frequencies
Instrument Setting
31 MHz
60.999999 MHz
4. Check the counter reading at the frequencies indicated.
• If the readings are within the limits specified, the probability is greater than 90%
that the fractional-N assemblies are functional. Either skip ahead to the
Generator Check" on page
Check with Oscilloscope"
• If the readings fail the specified limits, perform the
page 7-22.
A14 VCO Range Check with Oscilloscope
1. Remove the W9 HI OUT cable (A14J1 to A7) from the A7 assembly and connect it to an
oscilloscope set for 50 ohm input impedance. Switch on the analyzer.
2. Press
Preset System
activate the FRACN TUNE service mode. See
Error Messages,"
3. Vary the fractional-N VCO frequency with the front panel knob and check the signal
with the oscilloscope. The waveform should resemble
Figure 7-19.
If the fractional-N output signals are correct, continue source troubleshooting by
skipping ahead to
7-20
SERVICE MENU
ANALOG IN Aux Input
to set the analyzer to CW mode.
CW FREQ
Table 7-5
Counter Reading
30 ±0.030 MHz
60 ±0.060 MHz
7-25, or perform the more conclusive
described next.
SERVICE MENU
for more information on the FRACN TUNE mode.
"A7 Pulse Generator Check" on page
ANALOG BUS ON
to switch on the analog bus and
FRAC N
and see whether the VCO generates the
"A14 VCO Exercise" on
SERVICE MODES
Chapter 10 , "Service Key Menus and
Figure 7-17,
7-25.
Meas
"A7 Pulse
"A14 VCO Range
to
FRACN TUNE ON
Figure 7-18, and
Chapter 7