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7.
TROUBLESHOOTING
7.1
General Approach
When troubleshooting problems, a rational plan can save you many
hours of frustration. The following is a brief outline of standard
troubleshooting procedures.
1. Gather the facts to determine the exact nature of the problem.
2. Draw a picture of the system showing the equipment at both the
host and remote ends and the phone lines or in-house wiring.
Use this as a reference to note your observations, test steps and
test results. A picture keeps you focused and often saves
duplicate effort.
3. Record the front panel indications before changing anything.
This is an important part of fact gathering.
4. If you change anything, change only one thing at a time.
5. Use the built-in test functions, especially the loopback tests and
record your results.
7.2
Loopback Tests
It is best to begin loopback testing at the remote terminal and work
toward the host. If all the loopbacks are successful, the data
communications equipment and the terminal are working correctly.
Put the SPL Drop multiplexer port in loopback and have someone type
alpha characters on the keyboard of the affected terminal. If the data
appears correctly on the screen, the port is working. Next loop the
associated port of the host multiplexer. If data again appears correctly,
the communications link and the ports on both multiplexers are
working correctly. The problem then is with the host computer port or
the cable between the host computer and the multiplexer.
Loopbacks can be turned on and off from the Network Management port
of the SPL Drop multiplexer. See paragraphs 5.4.5 and 5.4.6 for details.
If a NMP terminal is not available, drop multiplexer port loopback can
be enabled using a DIP switch on the multiplexer. Refer to Figure 1
and paragraph 4.1.2.1 for switch location and operation.
