It it always best to consult a trained professional when fault finding as it can be very dangerous. do not attempt fault finding unless you know what you are doing.

Electronics fault finding is a process of illumination. A fault report is used to note action taken, results and comments on the next step. As you have probably guessed, digital and analogue have to be fault found in different ways.

All electronics fault finding needs some common sense, knowledge about how components act and react and experience.

Analogue Fault Finding
The first thing to do is a visual inspection. You're looking for any burned out components, dust or broken track. It also might be useful to calculate voltages in various places for later measurement matching.

Next, you'll need a fault finding report sheet that will look something like this:

	Results	Comments
Safety Test
Functional Test
Test 1
Test 2
Test 3
Conclusion/ fault found

Safety Test
This is a very important test as it separates you from killing yourself and or the appliance. A safety test makes sure the circuit won't draw too much current. This is done by doing a total resistance test of the circuit. If the result is wildly low, do not apply power.

Functional Test
This is identifying the problem. For example, if you were doing a functional test on a torch, you'd check if light was appearing; on a radio - if there is any sound and the LCD screen works. From there we can start testing.

Testing
In the example fault report, we have test 1, test 2, test 3. This would continue test 4, 5 etc depending on how many tests you need to do to find the fault. This is the part where experience is required. Start testing at the power supply and move around different parts of the circuit where errors are found and it should lead you to the final fault, perhaps a component. If a component is suspected to be faulty the next step is the 'component test'. A component resistance is simple measured to check for short or open circuits. It's very often that the failure of this component has also affected other components so final checks are needed.

Conclusion
Note the final fault in this section of the fault report and any other notes that might need to be given.[newpage]Flow Diagrams
Fault reports can also be shown in flow diagrams, an example is shown below.


Digital Fault Finding
This is slightly different from analogue fault finding as you mainly use a logic probe. Only two faults can be found - open circuit or short circuit. The fault report is stilled used but each test is a function test. When fault finding an IC (integrated circuit) we'd have a data sheet of known inputs and outputs and in turn test each one.

For example, applying +5 (1) to both inputs of an AND gate should output logic 1. You can then test for open or short circuit using a trace finder.