Telos TWOx12 - Page 158

TELOS TWOX12 USER’S MANUAL
TECHNICAL DATA & TROUBLESHOOTING
CHAPTER 8 146
• Observe collateral behavior to gain as much information as possible about the
problem;
• Round up the usual suspects;
• Generate a hypothesis;
• Generate an experiment to test the hypothesis;
• Fix the problem;
• Then, repeat, if necessary, to attack additional problems.
Let us now cover each step of the troubleshooting sequence in detail.
Step 1.
Observe the behavior to find the apparent bug. In other words, determine the bug's
symptoms. Remember always that many problems are subtle and exhibit themselves via a
confusing set of symptoms.
Step 2.
Observe collateral behavior to gain as much information as possible about the
problem. Does the LCD's problem correlate to an LED flashing? Try to avoid studying a
problem in isolation, but at the same time be wary of trying to fix too many at the same time.
No one is smart enough to deal with multiple problems all at once – unless they are all
manifestations of something more fundamental.
Step 3.
Round up the usual suspects. At the system level, always suspect the menu set-up,
the cables, the Phone Company line setup, the punch-blocks, etc. At the component level,
many computer problems stem from the same sources. Never, never, never forget to check
Vcc!
Step 4.
Generate a hypothesis. Before changing things, formulate a hypothesis about the
cause of the problem. You probably don't have the information to do this without gathering
more data.
Sometimes you will have no clue what the problem might be. Sometimes, when the pangs of
desperation set in, it's worthwhile to try anything practically at random. You might find a bad
plug, an unconnected line, or something unexpected. Look around, but be always on the
prowl for a working hypothesis.
Step 5.
Generate an experiment to test the hypothesis. Change the ISDN connection to a
known good line; call known good phone or hybrid at the other end; if long-distance doesn’t
work, try a local call.
NOTE:
You should plan your tests to eliminate 50% of the possible problems in one test, if
possible. Just keep careful track so you know what you have eliminated.
Step 6.
Fix the problem.
A Final Thought…
Constantly apply sanity checks. Twenty years ago the Firesign Theater put out an album
called "Everything You Know is Wrong". Use that as your guiding philosophy in
troubleshooting a Telos Two set-up. For example, just because you checked the Telco line
last night and it was fine does not mean that it's OK now.
At 3:00 AM when the problems seem intractable and you are ready to give up engineering,
remember that the system has worked and will work. Never panic–you are smarter than it is.