FC0-U71 Infrastructure Practice Question
A user reports that their desktop computer will not power on. The technician confirms the wall outlet works, the power supply switch is set to the correct voltage, and the power button cable is connected to the motherboard. When the technician presses the power button, no fans spin and no lights illuminate. Which component should the technician test next to determine whether the power supply is functioning?
⚠ Common exam trap
The trap here is jumping to motherboard or RAM replacement when the symptom of zero fan spin and zero lights most directly implicates the power supply.
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
When a desktop shows no fan movement and no lights despite a known-good outlet, the power supply is the most likely failure point. A PSU tester verifies the voltage on each rail without needing the motherboard to start. CMOS battery, RAM, and hard drive issues produce different symptoms and do not prevent the initial power-on sequence.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
RAM module
Why it's wrong here
Faulty or unseated RAM typically causes POST beep codes, no video, or repeated restarts, but the fans and power LED usually still activate. Total absence of fan spin and illumination points to a failure before the motherboard begins POST. Reseating or swapping RAM would not address a power delivery problem, so this step is not the appropriate next diagnostic action for a completely dead system.
- ✗
CMOS battery
Why it's wrong here
The CMOS battery maintains BIOS settings and the real-time clock when the system is unplugged. A depleted battery can cause lost time and configuration errors, but it does not prevent the system from powering on. Since no fans or lights activate, the issue is in the power delivery path, not in the low-voltage standby circuit that the CMOS battery supports, so testing it would not explain the symptom.
- ✗
Hard drive
Why it's wrong here
A failed hard drive results in boot errors or an inability to load the operating system, but the system still powers on with fans and lights. The scenario describes no power at all, which occurs before storage devices are accessed. Testing or replacing the drive would not resolve the no-power condition, so it is not a useful diagnostic step at this stage.
- ✓
Power supply tester
Why this is correct
A power supply tester connects to the PSU's main connectors and checks whether the rails output the correct voltages. When a system shows no signs of power at all, the PSU is a prime suspect. Using a tester on the 24-pin and CPU connectors quickly confirms whether the unit is dead or outputting out-of-spec voltages, allowing the technician to replace it or continue troubleshooting the motherboard.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This FC0-U71 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 FC0-U71 exam.