According to the CompTIA troubleshooting methodology, the next step after establishing a theory of probable cause is to test the theory to determine the cause. However, before testing the theory, the technician may need to conduct some research based on the symptoms and the possible cause. This may involve consulting online resources, manuals, documentation, or colleagues to find out more information about the power supply and how to test it. Research can help the technician confirm or eliminate the theory and avoid unnecessary actions or damage.
Answer A is incorrect because inquiring about environmental or infrastructure changes is part of identifying the problem, which is the first step of the troubleshooting methodology. The technician should have already done this before establishing a theory of probable cause.
Answer C is incorrect because establishing a plan of action to resolve the problem and implement the solution is the fourth step of the troubleshooting methodology. The technician should not jump to this step without testing the theory and verifying the cause.
Answer D is incorrect because documenting the findings, actions, and outcomes is the last step of the troubleshooting methodology. The technician should not do this until the problem is resolved and verified.
Reference: Troubleshooting Methodology | IT Support and Help Desk | CompTIA The technician thinks the power supply is defective, indicating an initial hypothesis but not a confirmed diagnosis. According to the CompTIA A+ Core 1 Study Guide, troubleshooting follows a structured methodology (Objective 5.5: "Given a scenario, troubleshoot problems related to motherboards, RAM, CPU, and power"). At this stage, the technician has likely identified the problem (PC failure) and gathered basic information (suspected power supply issue). The next step is to refine the theory by conducting research based on symptoms-such as checking for common power supply failure signs (e.g., no power, burning smell, or intermittent shutdowns)-before proceeding to action or documentation.
B: Conduct external or internal research based on symptoms: This involves verifying the hypothesis by reviewing symptoms against known power supply failure patterns, possibly consulting manuals, online resources, or past experiences. It ensures the technician's suspicion is grounded in evidence before proceeding.
A: Inquire about environmental or infrastructure changes: This is part of initial information gathering, typically done before forming a hypothesis, not after suspecting a specific component.
C: Establish a plan of action and implement the solution: Premature without confirming the power supply is the issue; action comes after testing the theory.
D: Document findings, actions, and outcomes: Documentation occurs after resolving the issue, not at this intermediate stage.
The study guide's troubleshooting steps prioritize research and theory validation after identifying a potential cause, making B the next logical step.
Exact Extracts from the Study Guide:From The Official CompTIA A+ Core 1 Study Guide (220-1101):
Section 5.5, Troubleshooting Methodology:
"1. Identify the problem... Gather information from the user, identify user changes, and perform backups if applicable."
"2. Establish a theory of probable cause (question the obvious)... Conduct external or internal research based on symptoms to refine your theory."
"3. Test the theory to determine cause... Once confirmed, move to planning and action."
"4. Establish a plan of action to resolve the problem and implement the solution."
"5. Verify full system functionality..."
"6. Document findings, actions, and outcomes."
Implication: After suspecting a power supply failure (step 1), the technician moves to step 2-researching symptoms-before testing or acting.
Section 5.5, Power Supply Issues:
"Power supply failure symptoms-No power, system won't boot, intermittent shutdowns, or a burning smell... Research common indicators online or in documentation to confirm the issue before replacing components." These excerpts show that researching symptoms follows the initial hypothesis and precedes actionable steps, aligning with option B.
Additional Reasoning:Current Stage: The technician has a theory ("defective power supply") but hasn't confirmed it. Research bridges the gap between suspicion and certainty.
Power Supply Symptoms: Symptoms like no power or random reboots need validation-e.g., checking if fans spin or if there's a capacitor failure-which research can guide.
CompTIA Methodology: The six-step process is sequential. Step 1 (identify problem) is done; step 2 (establish and research theory) is next, not jumping to action (step 4) or documentation (step 6).
Other Options:
A: Asking about changes (e.g., power surges) is part of step 1, likely already done to suspect the power supply.
C: Planning and implementing (e.g., replacing the PSU) requires a tested theory, not just a suspicion.
D: Documentation is the final step, not the next one after forming a hypothesis.
References:The Official CompTIA A+ Core 1 Study Guide (220-1101):
Section 5.5: "Given a scenario, troubleshoot problems related to motherboards, RAM, CPU, and power" (troubleshooting methodology and power supply issues).
CompTIA A+ Core 1 (220-1101) Exam Objectives:
Objective 5.5: Apply the troubleshooting process, including researching symptoms to confirm theories.

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References:
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