1. Circuit Analysis and Troubleshooting
A Six Step Procedure
Created by Jimmie Fouts
Houston County Career Academy for

2. Essential Question
How can a standardized approach toward electronic equipment troubleshooting save many hours of equipment downtime and costly repairs?

3. A Six Step Procedure?
A standardized approach toward electronic troubleshooting and maintenance:
Prevents equipment “down time”
Saves time needed for repairs when required
Ensures operation to design standards
Saves money!

4. The SIX-STEP Procedure
Use of a six-step procedure will provide a logical approach to trouble analysis
The six-step procedure is as follows:
1. Symptom recognition
2. Symptom elaboration
3. Listing of probable faulty functions
4. Localizing the faulty function
5. Localizing trouble to the circuit
6. Failure analysis

5. 1. Symptom Recognition
Determine if the equipment is functioning as designed. Is it normal or abnormal?
A trouble symptom is a sign or indicator of a malfunction
Use your senses of sight and hearing! Indicator lights, speakers, meters…smoke!
Look for degraded performance as well; degraded performance often leads to equipment failure
Know your equipment!

6. 2. System Elaboration
Observe any “built-in” indicators for more detailed information on symptoms
Obtain a detailed description of any trouble symptoms
Similar symptoms can be caused by similar faults!
Check front panel switches and control settings
What fault is probably causing the specific symptoms in question?

7. Symptom elaboration requires an evaluation of all observed displays
Indications must be evaluated in relation to each other as well as the overall operation
Record information observed! For example: How did each control affect an associated meter or other indicator?
“Think” about the information before jumping to a conclusion!

8. 3. List Probable Faulty Functions
Many equipments have more than one functional area or unit
“Where can the trouble logically be in order to produce the information gathered?”
For example: Your computer contains RAM, a motherboard, a processor, a power supply, a hard drive….. What functional area might be at fault?
Dividing the equipment into functional areas can save numerous trouble shooting steps

9. Functional Block Diagram!
Useful in the isolation of a fault!
Example:
Microphone: Converts sound energy into electrical energy at an audio frequency
Modulator: Amplifies the audio signal and sends it to the transmitter to change the carrier signal to be modified
Transmitter: Provides an amplified radio frequency (RF) signal to the antenna assembly
Antenna Assembly: Converts the electrical RF signal into an electromagnetic energy for transmission. It also receives electromagnetic energy and converts it into an RF signal for the Receiver Unit
Receiver Unit: Converts received RF signal into sound
Power Supply: Converts alternating (AC) voltage into suitable direct current (DC) for operation of the various units

10. 4. Localizing the Faulty Function
Up to this point, no test equipment has been required; only the equipment controls and indicators have been used
You can probably make a decision on where the most probable area for the malfunction is
Knowledge, skill, and proper test equipment should now be used to isolate the faulty functional area

11. Consider the Following Factors!
Which functional unit will give the best information for eliminating other units?
Which test points are more easily accessible?
What past experience and history do you have concerning similar faults with this particular equipment?
Are there other external units that may prevent proper operation of this unit?

12. 5. Localizing Trouble to the Circuit
More extensive troubleshooting is now required within the identified faulty unit
Isolate circuits within the faulty unit
Circuits and stages in circuit groups perform basic sub-function vital tasks
Look for improper voltages, improper waveforms, obvious component overheating
Isolate the defective circuit group!

13. 6. Failure Analysis
Steps 1 and 2 were used to recognize, verify, and obtain descriptive information
Step 3 allowed you to make a logical selection of the logical faulty unit
Step 4 provided for simple input-output tests and localized the faulty functions
Step 5 localized the fault to the circuit within the faulty unit
Step 6 will involve the actual replacement or repair of faulty circuit components

14. Schematic Diagrams
Illustrate the detailed circuit arrangement of electronic parts that make up complete circuits
Parts are represented symbolically
Show what is inside the “blocks” of the block diagram
Often provide voltage and resistance charts
Actual faults can generally be traced to one or several individual parts – resistors, capacitor, transistors, etc.

15. Complete, Degraded, Intermittent
Complete or abnormal performance of a component usually results in equipment failure
“Degraded” performance is the result of equipment not operating as designed or to design specifications
An intermittent part malfunction refers to something that stops operating, then begins operating again

16. Isolation of Faulty Parts
Observe the output signal of the circuit group
Voltage, duration, waveform shape
Conduct a visual inspection of parts and leads in the circuit
Look for burned parts or defective connections
Perform resistance checks
Ensure ALL power sources are OFF to the unit
Don’t expect identical readings to the schematic. Tolerances of as much as 20% may be acceptable.
Some equipments may require specialized test equipment. Refer to the Maintenance Manual.

17. BE AWARE of MULTIPLE FAULTS!
Often active components fail because of other components within the circuit
Common causes of failures may include:
Biasing resistor value changes causing a defective transistor
Defective capacitors failing to block DC current
Power surges from a power supply may cause burn-out of system components
Excessive current usage causing defective fuses
Intermittent faults that cause random failure

18. Return of Equipment to Operation
After replacing the faulty part or components always recheck equipment for proper operation!
Record your actions….they may be needed for future repairs!
Symptom Recognition
Symptom Elaboration
Listing of Probable Faulty Functions
Localizing the Faulty Function
Localizing Trouble to the Circuit
Failure Analysis