User's Manual Part 2
PN 8100-40 Help Hot Line (U.S. only): 1-800-530-9960 10-3
620004-0 Rev. E
Troubleshooting
10.2.1 Troubleshooting Guidelines
The following table contains troubleshooting information that the diagnostic LEDs do
not cover. Please check the table for a possible cause of a problem. Simple checks or
minor adjustments might eliminate the problem and restore proper operation.
Problem/Symptom Check
No downlink signal
output when all diag-
nostic LEDs are green
Make sure that there is a reasonable amount of power at the input of the Main Hub. Use a power
meter to measure the output power from the coaxial cable that feeds the Main Hub.
The LGCell is intended for a different frequency band. Verify that your system corresponds to the
desired frequency (for example, 800 MHz, 1800 MHz, or 1900 MHz).
Check the part number of each unit to be sure you have the proper band (e.g., DAS19M-4A-AD is
the part number for a Main Hub set up for 1900 MHz A and D bands).
The system gain is
lower than specifica-
tion
The optical fiber connector may be dirty. Clean the ST optical connector, using the manufacturer’s
recommended cleaning procedure.
There are two types of multimode fiber (MMF), 62.5µm/125µm and 50µm/125µm. Make sure the
vertical run of MMF is the 62.5µm/125µm type of fiber.
Check the length of MMF and UTP/STP cabling.
Remote Access Unit
(RAU) power LED
(green LED) stays off
after you plug in the
twisted pair cable
The Expansion Hub provides power to the RAU. Make sure the Expansion Hub is on.
Make sure that the twisted-pair (TP) cable wiring conforms to the TIA/EIA 568-A standard. Use a
standard local area network (LAN) cable tester to perform this test. Make sure the Cat-5 is not
plugged into the Expansion Hub when doing this test. Possible errors are incorrect wiring and/or
cable length.
The LGCell perfor-
mance is intermittent
when you use it for the
CDMA application
The uplink and downlink gains are not balanced. A CDMA system performs active power control
between the base station and the mobile unit. It is important to maintain a balanced link from the
base station ports to the RAU ports (equal uplink and downlink gain) to optimize the performance of
the LGCell.
Possible MMF port
problem on a Main
Hub
To isolate possible port problems on a Main Hub try moving the faulty fiber pair to another port on
the hub or to another Main Hub.
When you move an active fiber pair, the Main Hub remembers that there was fiber on that port and
issues an alarm. You must clear the latched alarm (port disconnect memory feature) by cycling Main
Hub power.
Possible RJ-45 port
problem on an Expan-
sion Hub
Move the Cat-5 to a spare port or swap the Cat-5 to try and isolate the problem.
The Expansion Hub also has port disconnect memory to track which ports have been connected. So
when a Cat-5 is disconnected and moved to a new port, an alarm will be issued. You must cycle
power to the Expansion Hub to clear the memory and the latched alarm.
If the Expansion Hub is suspect, try and remove all RAUs to eliminate any possible RAU failure and
then begin to put RAUs back in. Remember to cycle power whenever a RAU is removed.
Possible RAU prob-
lem
When working RAU problems, an RAU whose functionality has been confirmed can be used with
about 15 m (50 ft) of Cat-5 to quickly verify ports on an Expansion Hub. Simply connect the RAU to
one end of the cable and plug the other end into the Expansion Hub ports to verify proper operation.
Troubleshoot down-
link problem on an
active system
Downlink problems can be troubleshot on an active system by injecting a low-level signal at the
Main Hub using the unused port (either the duplex bidirectional port or the simplex downlink port).
Then you can go out to the RAU and perform some measurements without disrupting normal ser-
vice.