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220-1201 Power supply troubleshooting Practice Question
A customer complains that their computer will not turn on. The power supply fan does not spin, and the motherboard LED is off. The technician tests the power supply with a multimeter and gets 0V on all pins. What should the technician do next?
⚠ Common exam trap
Technicians often jump to replacing the PSU without verifying the power source first. A simple outlet check can save time and avoid unnecessary part replacement.
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
✓
Check the wall outlet with a voltage tester.
A multimeter reading of 0V on all PSU pins indicates no power output, but this could be due to a dead PSU or lack of AC input. The most logical next step is to verify the wall outlet is supplying power using a voltage tester. If the outlet is good, then the PSU is faulty and should be replaced. Replacing the PSU without checking the outlet first may not resolve the issue if the outlet is dead.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replace the motherboard.
Why it's wrong here
Replacing the motherboard is a premature and costly step when a computer fails to turn on, as it bypasses critical initial diagnostics. The motherboard is a downstream component that requires power from the power supply unit (PSU), which in turn receives power from the wall outlet. Troubleshooting dictates verifying the power source and the PSU's functionality first, as these are far more common failure points for a 'no power' symptom than the motherboard itself.
- ✗
Reseat the 24-pin power connector.
Why it's wrong here
Reseating the 24-pin power connector is generally not the initial troubleshooting step for a computer that exhibits no power whatsoever. If the computer 'will not turn on,' it implies a complete lack of power, suggesting a more fundamental issue with the power source or the power supply unit (PSU) itself. A loose 24-pin connector might cause intermittent power or failure to POST, but it's less likely to be the root cause of a total power outage compared to external power issues.
- ✗
Replace the power supply with a known-good unit.
Why it's wrong here
Replacing the power supply with a known-good unit, while a valid step if the PSU is suspected, is not the immediate next action for a 'no power' complaint. Before incurring the cost and effort of swapping components, it is essential to first confirm that the existing PSU is even receiving power from the wall outlet. Skipping this crucial diagnostic step can lead to unnecessary component replacement if the actual problem lies with the external power source rather than the PSU itself.
- ✓
Check the wall outlet with a voltage tester.
Why this is correct
Checking the wall outlet with a voltage tester is the correct and most logical first step when a computer fails to turn on. This action directly verifies the primary power source, confirming whether AC voltage is present and sufficient at the point of connection. This diagnostic step quickly rules out external issues such as a tripped circuit breaker, a faulty outlet, or a problem with the building's electrical wiring, thereby isolating the problem to either the external power source or the computer's internal power components.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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