At Least One Signal Path Looks Normal - Agilent Technologies 8719ET Service Manual

Receiver Troubleshooting

At Least One Signal Path Looks Normal

At Least One Signal Path Looks Normal
One normal signal path indicates that at least one sampler, one 2nd converter, A12, and
much of A10 are functional. Therefore, substitution is a convenient troubleshooting
approach. If two signal paths are abnormal, repeat the steps of this section for each
suspect signal path.
1. To see the traces of signal path A or R, connect a short to PORT 1 on ES models
(REFLECTION port on ET models).
Press the following:
Preset PRESET: FACTORY
INPUT PORTS
Meas
SERVICE MENU
System
MORE SAMPLR COR OFF
2. To see the traces of signal path B or R2 (if the instrument is an ES model Option 400),
connect a short to PORT 2 on ES models. On ET models, connect an RF cable to the
REFLECTION and TRANSMISSION ports. Then press the following:
PRESET: FACTORY
Preset
Meas INPUT PORTS
(
B TESTPORT 2
System SERVICE MENU
MORE SAMPLR COR OFF
3. For examples of the normal signal traces, refer to
trace nominal power levels, refer to
The illustrations depicting the analyzer display were made using an 8722ES
NOTE
model with nominal test port power. Other analyzer displays may appear
different, depending on model and options.
• Even if the R signal path trace is abnormal, the R sampler is nonetheless good (or
there would be a phase lock problem). Go directly to
page 8-9.
• If the A or B signal path is very low and the R signal path is normal, go to
Sampler Check by Substitution" on page
• If the A or B signal path appears slightly low, the problem is possibly a faulty
directional coupler or, more probably, a lossy sampler. To isolate the fault, continue
with "Directional Coupler Check" on page
8-4
Preset
, or
R A
SERVICE MODES
Preset
or
R
on ES models) ( on ET models)
B
SERVICE MODES
Table 8-2 on page
Figure 8-1 on page
8-5.
"2nd Converter Check" on
8-8.
8-7.
8719ET/20ET/22ET
8719ES/20ES/22ES
RF Network Analyzers
8-6. For signal
"A and B
Service Guide