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Difficulty: MediumMotherboard, RAM, CPU, and Power Issues

A technician is troubleshooting a custom desktop PC that shuts down immediately after the power button is pressed. The internal fans spin for less than a second, the power LED blinks once, and the system completely loses power. Pressing the power button again does nothing until the power supply's rocker switch is toggled off and on. Which of the following actions should the technician perform first to isolate the underlying cause of this issue? (Select TWO.)

  1. Disconnect non-essential expansion cards, internal drives, and front-panel USB headers to test for a short circuit tripping PSU protection.Answer
  2. B
    Reinstall the operating system onto the main boot drive to repair corrupted system startup binaries.
  3. Test the power supply output voltages using a dedicated PSU tester or multimeter to verify rail stability.Answer
  4. D
    Replace the installed desktop memory with SO-DIMM modules to resolve channel timing mismatches.

Answer

The technician should disconnect non-essential expansion cards and storage drives to isolate short circuits, and test the power supply output voltages using a power supply tester or multimeter.
The correct diagnostic actions involve isolating potential hardware short circuits by disconnecting non-essential peripherals and testing the power supply's voltage rails with a multimeter or dedicated tester. An instant shutdown where fans briefly turn on indicates a power supply short-circuit or over-current protection trip.

Step-by-Step Solution

1
Analyze the symptoms presented by the system.
The immediate power-off behavior (fans spinning briefly then shutting off) indicates a power supply protection mechanism (Over-Current Protection or Short-Circuit Protection) being triggered before POST.
Modern power supplies automatically shut off power when a short circuit or severe rail drop occurs, requiring a power cycle to reset.
2
Isolate potential short circuits from connected peripherals and internal hardware.
Disconnecting extra storage drives, expansion cards, and front USB connectors helps confirm whether an auxiliary hardware component is shorting a power line.
Minimizing system hardware identifies if the core platform (PSU, motherboard, CPU) is functional.
3
Verify the integrity of the power supply unit output.
Measuring output voltage rails (+12V, +5V, +3.3V) with a tester or multimeter determines if the PSU itself is defective.
A failing power supply with degraded capacitors will fail to maintain regulated voltages, causing instant thermal or voltage cutoffs.

Key Concept

Power supply unit (PSU) protection mechanisms and hardware short circuit isolation procedures
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Topics

Motherboard, RAM, CPU, and Power Issues

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