Troubleshooting and Fault Finding

Understanding Faults and Failures

In electronics, a fault is an abnormal condition or defect that hinders the normal operation of a device or system.
Failures are the manifestation of these faults, leading to misbehavior or complete shutdown of the device, system, or a subsystem.
Faults can be persistent (permanent) or intermittent (occurring irregularly).

Fault Finding Approaches

A systemic approach to fault finding involves understanding the device operation, symptom observation, and diagnostic testing.
Emphasise understanding the design and overall functionality of the device, as some faults can be predicted based on the design itself.
Symptom observation helps identify the faulty component or subsystem. It involves identifying changes in device behavior or performance.
Diagnostic testing thoroughly checks the operation of individual components and subsystems, helping isolate the specific fault location.

Tools for Troubleshooting

Basic troubleshooting tools include multimeters for measuring voltage, current and resistance, and oscilloscopes for viewing signal shapes and patterns.
Logic probes and logic analyzers can be used for digital circuits, checking logic levels (high/low) and sequences of these levels.
For more complex systems, hardware diagnostic tools and software debugging tools may be required.

Fault Classification

Faults can be categorised into different types, including short circuit faults, open circuit faults, component value faults and intermittent faults.
An open circuit fault is when a path is broken, disrupting the flow of current.
A short circuit fault occurs when a low-resistance path is established between two points that are not meant to be directly connected, which can cause excessive current flow.
Component value faults involve the change in the operating values or characteristics of components.
Intermittent faults are temporary and can be hard to detect as they occur unpredictably.

Mitigation Measures and Repairs

Once the fault is diagnosed, the next step is to repair or replace the faulty component or subsystem.
Mitigation measures can include designs for fault tolerance to allow the device to continue operation, even in a degraded state, until the fault can be fully addressed.
Regular maintenance and inspection reduces the chances of faults occurring and improves the longevity of the device.

Documentation and Reliability

Maintaining documentation of troubleshooting processes and findings helps future diagnoses and can improve design approaches.
Understanding, diagnosing, and fixing faults improves the reliability of electronic devices in the long-term.
The ultimate goal is not just to fix faults and failures, but to enhance the reliability and resilience of the entire system.