220-1101 Hardware and Network Troubleshooting Practice Question
A technician is troubleshooting a desktop computer that randomly restarts under heavy load, such as during video rendering. Temperature monitoring shows CPU and GPU temperatures are within normal ranges. The power supply unit (PSU) fan is spinning, but the technician suspects power delivery issues. Which tool should the technician use to directly test the PSU's voltage outputs?
⚠ Common exam trap
A common mix-up: candidates choose a multimeter (A) because they know it measures voltage, but they overlook that a power supply tester is the specialized tool designed for safe, direct, and comprehensive PSU output testing without needing to power on the entire system.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Power supply tester
A power supply tester (D) is the correct tool because it is specifically designed to measure the voltage outputs of a PSU on each rail (e.g., +3.3V, +5V, +12V) under load conditions, directly verifying if the PSU is delivering stable power. While a multimeter can also measure voltage, it requires the technician to probe live pins while the system is running, which is less safe and does not simulate load as effectively. The power supply tester provides a dedicated, safe, and accurate way to test PSU output without needing to power on the entire system.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Multimeter
Why it's wrong here
While a multimeter can measure DC voltage, using it on a power supply requires the technician to manually identify the correct pins on the 24-pin ATX connector, insert probes while the system is under load, and interpret readings without any load simulation. That process is slower, more dangerous (risk of shorting pins), and gives only point-in-time measurements, whereas a dedicated power supply tester provides safe, load-based, continuous rail readings ideal for diagnosing random restarts.
When this WOULD be correct
A multimeter would be correct if the question asked for testing voltage at a wall outlet, verifying continuity of a power cord, or measuring resistance of a component. For example: 'A technician needs to verify that a wall outlet provides correct AC voltage. Which tool should be used?'
- ✗
Loopback plug
Why it's wrong here
A loopback plug is a diagnostic tool for network interface cards that routes transmitted signals back to the same port's receiver to validate the NIC's ability to send and receive data. It does not connect to any power supply rail or sense voltages, so it is completely incapable of detecting the brownout, ripple, or rail fluctuation in a PSU that triggers spontaneous reboots.
When this WOULD be correct
A technician needs to verify that a network interface card (NIC) is functioning correctly after driver installation. Using a loopback plug on the NIC port allows the technician to run a loopback test to confirm the port can send and receive data.
- ✗
Cable tester
Why it's wrong here
A cable tester is designed to verify the integrity of twisted-pair Ethernet or coaxial cabling by checking pin-to-pin continuity and detecting wiring faults such as opens, shorts, or reversed pairs. It has no connectors or circuitry capable of measuring the DC voltage levels on a PC power supply, so it cannot identify the unstable or failing PSU rails that commonly cause random restart loops.
- ✓
Power supply tester
Why this is correct
A power supply tester plugs directly into the ATX, EPS, and peripheral connectors of a PSU and displays the actual voltage on each rail (e.g., +3.3 V, +5 V, +12 V) under a small load. This makes it the fastest and most reliable tool for confirming whether the PSU is delivering stable, within-tolerance power, which is the critical first check when a desktop randomly restarts due to power delivery faults.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓Power supply testerCorrect answer▾
Why this is correct
A power supply tester plugs directly into the ATX, EPS, and peripheral connectors of a PSU and displays the actual voltage on each rail (e.g., +3.3 V, +5 V, +12 V) under a small load. This makes it the fastest and most reliable tool for confirming whether the PSU is delivering stable, within-tolerance power, which is the critical first check when a desktop randomly restarts due to power delivery faults.
✗MultimeterWrong answer — click to see why▾
Why this is wrong here
A multimeter can test voltage outputs, but it requires the PSU to be disconnected from the motherboard and powered on, which is unsafe and impractical for a desktop under load. The question asks for a tool to directly test the PSU's voltage outputs, and a power supply tester is designed specifically for this purpose with safe connectors and load simulation.
★ When this WOULD be the correct answer
A multimeter would be correct if the question asked for testing voltage at a wall outlet, verifying continuity of a power cord, or measuring resistance of a component. For example: 'A technician needs to verify that a wall outlet provides correct AC voltage. Which tool should be used?'
Why candidates choose this
Candidates know multimeters can measure voltage, so they assume it can test PSU outputs. They may not realize that a standard multimeter cannot safely simulate the load needed for accurate PSU testing under heavy load conditions.
✗Loopback plugWrong answer — click to see why▾
Why this is wrong here
A loopback plug is used to test network ports by sending data back to the device, not to measure PSU voltage outputs. It cannot assess power delivery or voltage levels.
★ When this WOULD be the correct answer
A technician needs to verify that a network interface card (NIC) is functioning correctly after driver installation. Using a loopback plug on the NIC port allows the technician to run a loopback test to confirm the port can send and receive data.
Why candidates choose this
Candidates may confuse 'loopback' with a diagnostic tool for testing hardware outputs, or they might think it can be used to test power by creating a load, but it is specific to network signaling.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 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 220-1101 exam.