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    psu

    PC Power Supply (PSU) Problems

    Quick Answer

    This guide helps diagnose power supply issues in desktop PCs, from complete failure to boot to intermittent shutdowns and instability.

    Please note: This guide is provided for informational purposes only. Any steps you choose to follow are at your own discretion and risk. If you're unsure, we recommend booking a professional diagnosis.

    Quick Checks

    Try these fast checks first — they solve most cases.

    1. 1

      Check power cable

      Ensure the mains cable is firmly connected to the PSU and wall outlet.

    2. 2

      Test the wall outlet

      Plug another device into the same outlet to verify it works.

    3. 3

      Check PSU switch

      Ensure the PSU power switch on the back is in the ON position.

    4. 4

      Listen for fan spin on startup

      If PSU fan does not spin at all, the PSU may be dead.

    Guided Troubleshooting

    Answer these questions to narrow down the issue.

    Does the PC show any sign of life when pressing power?

    Does the PC shut down randomly under load?

    Do you smell burning from the PSU area?

    Possible Causes

    Faulty power cable

    Common

    Damaged or loose mains cables prevent power delivery.

    PSU failure

    Common

    Capacitors and components inside PSUs degrade over time.

    Insufficient wattage

    Moderate

    Upgraded GPU or CPU may exceed PSU capacity.

    Faulty PSU switch

    Less Common

    The rear switch can fail or have poor contact.

    Overheating PSU

    Moderate

    Dust buildup or poor ventilation causes PSU to overheat and shut down.

    Damaged internal cables

    Less Common

    Modular PSU cables can become damaged or loose.

    If the cause requires professional attention, see Get Desktop PC wont turn on fixed.

    Self-Fix Instructions

    Safe steps you can try at home.

    Paperclip test

    1. Unplug PSU from all components. 2. Find the 24-pin motherboard connector. 3. Bridge the green wire (PS_ON) to any black wire (ground) with a paperclip. 4. Plug PSU into wall and switch on. 5. If fan spins, PSU has basic power. If not, PSU is dead.

    Check all internal connections

    1. Power off and unplug. 2. Reseat the 24-pin motherboard connector. 3. Reseat the 4/8-pin CPU power connector. 4. Check GPU power connectors. 5. Ensure all modular cables are firmly connected at both ends.

    Test with minimal components

    1. Disconnect everything except CPU, one RAM stick, and motherboard power. 2. Try to boot. 3. If it works, add components back one at a time. 4. This isolates which component is causing the issue.

    Calculate power requirements

    1. Use an online PSU calculator. 2. Add up all component power draws. 3. Add 100-200W headroom. 4. If your current PSU is below this, upgrade. 5. Choose 80 PLUS Bronze or Gold rated units.

    Replace the PSU

    1. Purchase a PSU with adequate wattage and good rating. 2. Power off and unplug the PC. 3. Disconnect all PSU cables from components. 4. Remove old PSU from case. 5. Install new PSU and reconnect all cables.

    Safety Warnings

    • Never open a PSU. Internal capacitors hold dangerous charge even when unplugged.
    • If you smell burning, unplug the PC immediately and do not use it.
    • A failing PSU can damage other components. Replace promptly if issues are confirmed.
    • Always use the cables that came with your PSU. Do not mix cables between different PSU models.

    When troubleshooting isn't enough

    If these steps didn't resolve the issue, a professional diagnosis can identify the root cause.

    FixFix Labs is not responsible for pre-existing data loss or undisclosed damage.

    All repairs carry inherent risk. Complex or liquid-damaged devices may have unpredictable outcomes.

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