User's Manual

Basic Troubleshooting: RF Path Fault Isolation – continued
FEB 2005 1X SC 4812T Lite BTS Optimization/ATP 6-15
PRELIMINARY
Verify BLO Check Box
When performing a Calibration with the TX Calibration... or All
Cal/Audit... Functions, the Verify BLO Check Box should normally be
checked. When a Calibration fails, determine if any items such as
Directional Couplers or Combiners have been added to the TX Path.
If additional items have been installed in the path, try re–running the
Calibration with Verify BLO unchecked. If Calibration still does not
pass, refer to the following paragraphs and use the TX Output Fault
Isolation Flowchart to identify the most probable cause of the failure.
Single–Sided BLO Check Box
When performing a Calibration with the TX Calibration... or All
Cal/Audit... Functions, the Single–Sided BLO Check Box should not
be checked when the Redundant BBX is being calibrated. When a
Calibration fails with the Redundant BBX selected, try re–running the
Calibration with the Single–Sided BLO Check Box unchecked.
– If the Calibration still fails, refer to the following paragraphs and
use the TX Output Fault Isolation Flowchart to identify the most
probable cause of the failure.
If Faults Are Isolated
If the Fault Reports are isolated between successful Path Checks, the
root cause of the faults most likely lies with one or more of the Field
Replaceable Unit (FRU) cards/modules.
– If more than one failure was reported, look for a common
denominator in the data. For example, if any TX Test fails on one
sector only, the BBX assigned to that sector (Table 1-5) is a likely
cause. Also, look at the Severity of the failure.
– If the Path Loss is just marginally out of the relaxed specification
limit during the Post-Calibration TX Audit, suspect excessive Test
Cable Insertion Loss.
– If limits are missed by a wide margin, suspect incorrectly wired
cables or total device failure.
Use the TX Output Fault Isolation Flowchart in Figure 6-1 to identify
the strongest possible cause for a failed TX Test.
Fault Isolation Flowchart
The flowchart covers the Transmit Path.
– Transmit Paths usually fail the lower Test Limit, indicating
excessive Loss in some component in the BTS Site or incorrect
wiring.
– A failure of an upper Test Limit usually indicates a problem with
the Test Set–up or external equipment.
Before replacing a suspected FRU, always repeat and verify that the test
results to rule out a transient condition. If a BBX fails an Upper Limit in
the Post–Calibration Audit Procedure, re–calibrate and verify that the
out–of–tolerance condition for that BBX and/or sector before
replacement.
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