Fluke DSP-2000 - Manual (Page 133)

Basic Cable Testing
Troubleshooting Basics
7
7-21
Troubleshooting Basics
Troubleshooting LAN cable installations is most often required during cable
installation or modification. When cable is handled carefully and installed
correctly, it usually operates trouble-free for years.
Finding Cable Faults
A general rule for finding cable faults is as follows: With very few exceptions,
faults occur at cable connections. Cable connections include telecommunication
outlets, patch panels, punchdown blocks, and transition connectors.
Connections are the most likely places for faults for at least three reasons: (1)
Connections always alter the impedance of the transmission path, (2) connections
are likely places for faults caused by wiring errors and faulty or incompatible
hardware installation, and (3) connections always cause some crosstalk due to the
untwisting of cable pairs.
When cable is handled carelessly, faults can occur in the middle of the cable.
These faults can happen when the cable is stepped on, sharply bent, pinched by
cable ties or other hardware, or otherwise stressed.
A general procedure for finding cable faults (excluding sources of noise and
traffic faults) involves the following steps:
1. Run an Autotest on the cable.
2. Analyze the results of failed tests and determine a probable cause for the
failure. If you are using Model DSP-2000, press
F for specific information
on the fault.
3. If the Autotest results do not indicate the location of the fault, run an
additional test (such as TDR or TDX analyzer) that will help you locate the
fault. Model DSP-2000 provides these test results on its diagnostics displays.
4. Visually inspect the cable at the location indicated by the tests.
5. Repair the fault and retest the cable.
Table 7-1 on the next four pages shows possible causes for test failures and shows
examples of displays from tests that can help you locate the cause of a failure.