4-5. TROUBLESHOOTING PHASES
Each of the five phases in this routine is designed to accomplish a specific goal.
a. Fault Discovery. Usually, the operators or supervisor will notice faulty
performance first. They must report the fault on the proper form so you will have
the facts you need for the next phase.
b. Failure Confirmation. Based on the facts provided, you must confirm the
failure and define the symptom. The symptom is the first clue you will use in the
c. Troubleshooting Entry. Using the symptom defined during phase two, find the
troubleshooting flow chart which will help you isolate the fault in the equipment.
The checkout and symptom index chart (chart-00) will help you do this.
d. Trouble Isolation. Follow the step-by-step procedures in the flow chart to
isolate and correct the cause of the equipment failure.
After Maintenance. When you have made the fix recommended in the trouble-
shooting procedure, you must check your work. Go back to the chart titled Modem
Checkout/Symptom Index. It tells you how to test your repair and make sure the
equipment now works as it should.
4-6. ALTERNATIVE TROUBLESHOOTING TECHNIQUES
When a failure causes a symptom which is not covered in the symptom index or not
corrected by the troubleshooting procedure in the flow chart, you must try
a. Understand Principles of Operation. Sometimes the symptom may have no
specific procedure given to troubleshoot it. When this happens, remember that the
equipment always operates the same way. By comparing the faulty operation with
expected or normal operation you may find the cause of the failure and be able to
b. Check the Circuits. All electronic equipment uses circuits to route power
through the components. Any break in continuity will cause some type of failure.
By running continuity checks on suspect circuits you may find the cause of the
failure. Use the foldout schematic diagram at the rear of this manual to check the
circuits in this equipment.
c. Check Past Maintenance Records. If the unusual failure occurred before, it
should appear in the maintenance records for the equipment. The records should
also tell you how the failure was corrected. Use the same fix this time.
d. Trial and Error Repair. Usually trial and error repairs should be avoided.
They are costly and can induce additional symptoms. However, when your experience
with the equipment leads you to suspect a definite cause, you should try the repair
as a last resort before shipping the equipment to depot for maintenance.
4-7. TROUBLESHOOTING PROCEDURES
The troubleshooting procedures are arranged as flow charts. The charts consist of
background information, specific instructions and decision points. Symbols (table
to organize the charts and
through a step-by-step trouble
isolation procedure for each known failure symptom.