
Troubleshooting and Block Diagrams 8712ET/ES and 8714ET/ES
Category 2 Failures: No Error Messages but One or More Measurements Are Nonfunctional RF Network Analyzers
4-28 Service Guide
Symptom 4: R and R* Traces Are Always Below −10 dBm or Noisy
If other traces are normal, something in the R signal path could be damaged.
1. Check the power level out of the coupled port on the R coupler.
a. If the power level is below −20 dBm, replace the R coupler (refer to “Removing the
Coupler” on page 3-15).
b. If the power level is above −20 dBm, replace the receiver PC board from the receiver
assembly (A5). (Refer to “Removing the Receiver PC Board” on page 3-14.)
Symptom 5: A, B and B* Traces Are Always Below −10 dBm for the Forward and/or the Reverse Signal
Directions
If other traces are normal, this indicates a failure in the switch or the attenuator. A failure
in the switch is the more likely problem.
1. If the symptom exists in both the forward and reverse directions, check the power level
out of the attenuator.
a. If the power level is below −5 dBm, replace the attenuator (refer to “Removing the
Attenuator (ES and Option 1E1 Analyzers)” on page 3-16).
b. If the power level is above −5 dBm, replace the switch (refer to “Removing the Switch
(ES Analyzers)” on page 3-16).
2. If the symptom exists in only one direction, replace the switch.
Symptom 6: B and B* Traces Are Always Below −10 dBm and/or Are Always Noisy
This failure indicates a problem with the coupled signal from the B coupler.
1. Check the power level out of the coupled port on the B coupler (PORT 2 open, reverse
direction).
a. If the power is below −20 dBm, replace the B coupler (refer to “Removing the
Coupler” on page 3-15).
b. If the power is above −20 dBm at the coupled port, replace the receiver PC board
from the receiver assembly (A5). (Refer to “Removing the Receiver PC Board” on
page 3-14.)
Symptom 7: A Trace Is Always Below −10 dBm and/or Is Always Noisy
This failure indicates a problem with the coupled signal from the A coupler.
1. Check the power level out of the coupled port on the A coupler (PORT 1 open, reverse
direction).
a. If power is below −20 dBm, replace the A coupler (refer to “Removing the Coupler” on
page 3-15).
b. If the power is above −20 dBm at the coupled port, replace the receiver PC board
from the receiver assembly (A5). (Refer to “Removing the Receiver PC Board” on
page 3-14.)
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