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ProblemCannot stay powered on to boot

PC turns on then immediately shuts off

Pressing power produces a brief response, then the PC shuts off before it can boot. Start with external power and recent changes. If it stays on without video, use the no-display guide instead.

Try this first

2 quick checks · ~4 min

  1. Check the external cord and powerStart without opening the case.
  2. Disconnect nonessential external accessoriesIsolate peripherals without removing internal components.

Diagnostic signals

ObservationPower response is only momentary
Note whether it stays off or loops through starts; do not repeatedly press power to force a boot.
ObservationStarted after building or modifying the PC
Check compatibility and assembly against the manuals. The timing directs the inspection but does not prove which component is wrong.

Step-by-step solutions

01

Check the external cord and power

  • Estimated time: 2 min
  • Easy
  • Low risk

Start without opening the case.

  1. With the PC off and unplugged, check the external power cord for a secure connection and visible damage.

  2. If safe, use a known-working outlet and check the rear power switch if fitted. Do not change voltage selectors.

Sources:
02

Disconnect nonessential external accessories

  • Estimated time: 2 min
  • Easy
  • Low risk

Isolate peripherals without removing internal components.

  1. With power disconnected, remove USB hubs, external drives and recently added accessories. Keep only what is needed to observe startup.

  2. Reconnect power and make one attempt. If it stays on, shut down normally before reconnecting accessories one at a time. Stop testing if power cuts out again.

Sources:
Advanced

Advanced checks

Continue if the earlier steps did not help. Read each procedure’s precautions first.

03

Review the build documentation

  • Estimated time: 5 min
  • Intermediate

Do not start by reinstalling Windows for an early power cut.

  1. If hardware changed, compare CPU and RAM against motherboard support lists and check required BIOS versions. Do not flash BIOS while the PC is shutting off.

  2. Have cooling, assembly, power connections and front-panel wiring checked against the manual. Do not bridge pins with a screwdriver.

Sources:
04

Arrange internal inspection

  • Estimated time: 5 min
  • Intermediate

The next test requires familiarity with the hardware.

  1. If external checks do not help, ask for motherboard, cooling, memory and PSU assessment with known-compatible hardware. Do not buy parts based only on the symptom.

  2. Before internal work, shut down, disconnect power and follow the manufacturer’s procedure for residual power and electrostatic protection. If unfamiliar with it, do not open the case.

Sources:
Next step

Still not working?

Give the service technician motherboard/PSU models, recent changes and a description of startup behavior. A PC that cannot stay powered on needs hardware assessment, not a blind operating-system reinstall.

Sources

Documentation behind this guide. Editorial recommendations are identified separately.

Source review: . A documentation review, not a physical hardware test.

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