CompTIA A+ Core 1 (220-1201)Hardware and Network TroubleshootingMedium
A user reports that their desktop computer occasionally fails to power on completely. When the power button is pressed, the fans briefly spin, and some lights flash, but then everything shuts down. This happens inconsistently. Which component is the MOST likely cause?
- ACorrupted BIOS/UEFI firmware.
- BFaulty CPU.
- CFailing Power Supply Unit (PSU).
- DDefective RAM module.
Show answer & explanationAnswer & explanation
Correct answer: C. Failing Power Supply Unit (PSU).
If a computer briefly attempts to power on (fans spin, lights flash) but then immediately shuts down, especially inconsistently, it's a classic symptom of a failing power supply unit (PSU). The PSU may not be able to deliver enough stable power to fully initiate the boot process.
Why the other options are wrong
- A. Corrupted BIOS/UEFI firmware would typically prevent POST entirely or cause specific boot errors, not a brief power-on followed by shutdown.
- B. A faulty CPU would typically result in no POST or constant reboots, but usually not a brief power-on then immediate shutdown.
- D. A defective RAM module usually causes POST beep codes, system crashes, or failure to boot past the initial stages, not a brief power-on then immediate shutdown.
PSU Power-On Failure
A power supply unit that cannot provide the necessary stable power to fully initiate and sustain the computer's boot sequence.
- Symptoms include fans briefly spinning, lights flashing, then immediate shutdown.
- Often intermittent and worsens over time.
- Can be caused by component degradation within the PSU.
Memory trick: If the power flickers and dies, the 'supply' is telling lies.