THE BLUE BOX LT SYSTEM START-UP & CABLING GUIDE 101
HARDWARE ACTIvATION TROUBLESHOOTING
!
Always re-check “failed” results. If improperly set or
connected a meter can display unusual readings.
!
The “Bus-Splitting Technique” is the fastest way to find
a bad cable and/or damaged device. Be sure to docu-
ment the cable path!
!
Cat. 5 cables that pass a LAN cable test can still short
or break from stress and strain during installation.
If re-testing a suspected cable, roughly wiggle and tug the
conductors near the RJ45 while keeping an eye on the
LAN tester: conductors should remain properly engaged
throughout the test.
CONTINUITY TEST TROUBLE SHOOTING
Fluctuating resistance readings indicate one or more 1.
“active” devices are still “hot”. De-power all devices
and re-test.
High resistance readings indicate broken or resis-2.
tive connections. Use the “Bus-splitting” technique to
find:
RJ45 connectors not properly pushed into sockets •
(check to make sure that the wires are not ex-
tended beyond the end of the RJ45 connector)
Cable strain can break conductors or pull conduc-•
tors out of RJ45 contacts (visually inspect cable
and connector).
Unseated RJ45 sockets (rough install• environ-
ment)
Damaged device (rare)•
Dirt or paint on RJ45s (rare)•
Bad data/power jumper cable (rare)•
SHORT CIRCUIT TEST TROUBLE SHOOTING
A low resistance reading indicates a crossed or short-1.
ed pair or (rarely) a damaged device. Cable strain
when pushing switches into a wall can short nicked
conductors. Use the bus splitting technique to find
the bad cable, crimp or device.
Resistance readings below 3002. Ω on A-B only indicate
an extra terminator. Use the bus splitting technique
to find the short or extra terminator.
After the problem has been resolved, please com-3.
plete the “Continuity Test” again.
EARTH GROUND TROUBLE SHOOTING
LAN-tested cables can still have a path to earth ground.
An abraded or “folded” cable inside the conduit will 1.
cause a short to earth ground.
Other low voltage or high voltage wires touching any 2.
device on the bus will cause continuity to earth ground
Use the Bus Splitting Technique to locate the problem.
TERMINATOR TROUBLE-SHOOTING
Ensure that the Data/Power Jumper is removed.1.
Visually inspect both terminators are present and 2.
properly seated on each bus-end device.
ERROR CHECk TROUBLESHOOTING
If the hardware activation tests have just been completed
and the bus is unstable, consider the following causes:
Failure to follow the 568A or 568B color code (or 1.
minimally to use a dedicated pair for the center pins)
will cause the Error Check test to fail. Visually inspect
RJ45 connectors.
Occasionally, the flat-cable connecting the clock to 2.
the master panel can become damaged. Visually in-
spect the Cat. 5 cable – if damaged, replace it with a
new cable.
An external source of EMF (electromagnetic fre-3.
quency) or RF (radio frequency) interference may
be present and affecting the bus (or digital de-
vices). Refer to the beginning of this guide on run-
ning low voltage cables across or parallel to line
voltage cables or exposing low voltage cables to
EMF or RF sources (e.g. welders, ballasts, improp-
erly grounded wireless devices, etc.); any of which
can interfere with the bus operation and stability.
Visually inspect and handle any external sources of
signal noise - a digital device can also become dam-
aged and create signal noise.
An oscilloscope can be used to locate the source of the
bus failure. The “Oscilloscope Test” can be found in The
Blue Box LT “O&M Manual”.
If unfamiliar with how to use an oscilloscope or if one is
unavailable on-site, contact Tech Support: 1-800-345-4448.
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