Step 8: Troubleshooting Overview

black transistor beside capacitor

Eliminate the devices that could not cause this output.

This post is part of a series describing the generic, high-level troubleshooting process.

Previous Posts:
What is Troubleshooting?
Simplified Troubleshooting Overview
Step 1. Understand the correct inputs and outputs of the “black box.”
Step 2. Determine which output(s) are incorrect.
Step 3. Figure out which input(s) affect that output(s).
Step 4. Verify that those inputs are as expected.
Step 5. Analyze the path(s) from input(s) to output(s).
Step 6. Check all connections.
Step 7. What are the devices in those path(s) that change the data?

Next Posts:
Step 9. Test the remaining devices.
Step 10. Repair/Replace faulty device(s).
Step 11. Fully test the system.

Step 8. Eliminate the devices that could not cause this output.
In the last step, we determined everything that could change the data in the path that is having issues. In this step, we will eliminate any of those that could NOT cause the issue that we are seeing.

It is very possible that you will not be able to eliminate anything at all. Be very conservative in the things that you eliminate, if you are not, you may eliminate the item that is the problem. Just because it shouldn’t be able to cause that, doesn’t mean that it can’t.

Some possibilities are:

  • If the output voltage is higher than the input voltage, it’s probably not an issue with a connector, switch, relay, or wire (unless there’s a short). If the output voltage is lower than the input, it very much could be one of these.
  • I started a bullet list, but I really can’t think of anything else that would apply in most situations. There may be more in your situation.

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