Agilent Technologies 8752C, Руководство по обслуживанию, Страница: 294 / 510

Check Input Trace
All inputs to the sampler have been veried except for the signal coming from
the coupler . The problem is most likely a faulty coupler or sampler . However ,
the A10 assembly may also be at fault.
Press 4 PRESET 5 4 MEAS 5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
INPUT PORTS and select the input with the bad trace .
The trace normally has a number of jumps in it due to band switches , as shown
in Figure 8-1 through Figure 8-3. Each jump should be less than 2 dB .
If there are other peaks or holes in the trace , the sampler is probably faulty .
Remove the suspected sampler and exchange it with the known good sampler .
If the problem disappears , replace the suspected sampler .
If there is a broadband problem, it is probably caused by the coupler .
If the level (average value) of the trace is wrong but the trace is otherwise
correct, the problem is most likely in the coupler or the A10 assembly .
Either measure the output of the coupler with a power meter , or swap the
A10 assembly with another known working A10 assembly .
Check directivity , source match, and crosstalk by performing the
system verication procedure described in the \System V erication and
P erformance T ests" chapter . If any of these fail, check the coupler and
sampler connections .
T o verify the coupler is faulty , remove the sampler that has the bad input
and exchange it with the known good sampler . If there is no improvement,
replace the coupler . If the problem disappears , replace the original sampler .
If the 2nd LO is good at the sampler/mixer , the sampler/mixer assembly is faulty .
Otherwise , troubleshoot the A12 assembly and associated signal path.
8-14 Receiver T roubleshooting