The answer is a multimeter. This is the correct tool because it directly measures DC voltage output from the power supply’s connectors, allowing you to verify that each rail (e.g., +12V, +5V, +3.3V) stays within the ATX specification’s ±5% tolerance under load, which is critical when diagnosing intermittent shutdowns during gaming. On the CompTIA A+ Core 1 220-1201 exam, this question tests your ability to distinguish between diagnostic tools: a multimeter provides precise voltage readings, while a PSU tester only checks for basic connectivity and may miss voltage sag. A common trap is choosing a loopback plug, which only forces the PSU to turn on without measuring actual output. To remember, think “multi-meter measures millivolts,” and always test under load—like during a game—to catch a failing unit that drops voltage when stressed.
220-1101 Power Supply Practice Question
This 220-1201 practice question tests your understanding of power supply. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A customer reports that their desktop computer randomly shuts down after a few minutes of gaming, but it runs fine during light tasks. You suspect the power supply is failing. Which tool should you use to confirm the power supply's output voltages are within ATX specification?
Why wrong: A power supply tester only checks for correct pin voltages and signals, not precise voltage levels under load, so it may not detect marginal failures.
B
A multimeter
A multimeter can measure DC voltage on each rail (e.g., +12V, +5V, +3.3V) while the system is running, confirming if voltages are within ATX tolerances.
C
A loopback plug
Why wrong: A loopback plug is used to test USB ports or network interfaces, not power supply voltages.
D
An ESD strap
Why wrong: An ESD strap protects components from electrostatic discharge but does not measure voltages.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A multimeter
A multimeter is the correct tool for measuring DC voltages from a power supply. The ATX specification defines acceptable voltage ranges (e.g., +12V ±5%), and a multimeter can verify these under load. Other tools like a PSU tester or loopback plug may indicate basic function but don't measure actual voltage levels accurately.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
A power supply tester
Why it's wrong here
A power supply tester only checks for correct pin voltages and signals, not precise voltage levels under load, so it may not detect marginal failures.
✓
A multimeter
Why this is correct
A multimeter can measure DC voltage on each rail (e.g., +12V, +5V, +3.3V) while the system is running, confirming if voltages are within ATX tolerances.
Related concept
Read the scenario before looking for a memorised answer.
✗
A loopback plug
Why it's wrong here
A loopback plug is used to test USB ports or network interfaces, not power supply voltages.
✗
An ESD strap
Why it's wrong here
An ESD strap protects components from electrostatic discharge but does not measure voltages.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 220-1201 question in full detail.
Identify which 220-1201 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Power Supply — This question tests Power Supply — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A multimeter — A multimeter is the correct tool for measuring DC voltages from a power supply. The ATX specification defines acceptable voltage ranges (e.g., +12V ±5%), and a multimeter can verify these under load. Other tools like a PSU tester or loopback plug may indicate basic function but don't measure actual voltage levels accurately.
What should I do if I get this 220-1201 question wrong?
Identify which 220-1201 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is diagnosing a PC that will not power on. The multimeter shows 0V on all pins of the 24-pin connector when the PSU is plugged in and the power switch is on. What is the most likely cause?
hard
A.The motherboard is shorted, preventing the PSU from starting.
B.The power supply is completely dead and needs replacement.
✓ C.The AC power cord is loose or the wall outlet is dead.
D.The front panel power switch is faulty.
Why C: If no voltages are present, the PSU is not receiving AC power or its internal circuits are dead. The technician should check the AC outlet, power cord, and PSU switch first before concluding the PSU is faulty.
Variation 2. A desktop PC fails to power on. The technician measures the voltage on the 24-pin motherboard connector and finds that the purple wire (5VSB) reads 4.9V, but the green wire (PS_ON) reads 0V when the power button is pressed. What does this indicate?
hard
A.The power supply is faulty and needs replacement.
✓ B.The motherboard is not sending the PS_ON signal, likely due to a fault.
C.The power supply's +12V rail is shorted, causing overcurrent protection.
D.The front panel power switch is stuck in the closed position.
Why B: The green wire (PS_ON) is pulled low by the motherboard to start the PSU. If it stays at 0V, the motherboard is not signaling the PSU to turn on. The 5VSB being present means the PSU's standby power is working, isolating the issue to the motherboard or front panel switch.
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This 220-1201 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1201 exam.
Question Discussion
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