New PC Won't Turn On: Power and Front-Panel Checks

1. Separate no power from no picture

Watch for lights, a fan twitch, repeated cycling or steady operation. A standby LED shows that some power reaches the board, but it does not prove that the system can start. A PSU fan that stays still is inconclusive too; some supplies stop their fan at low load. If the PC stays on and only the picture is missing, move to the no-display guide. If it does nothing or stops immediately, continue here and note the exact response before changing a connection.

2. Check the external supply path

Test the outlet with a known working appliance and check the switch on any power strip. Inspect the mains cable for damage and make sure it is seated at both ends. Check the PSU's rear switch if it has one. A replacement mains lead must have the right connector and electrical rating. If connecting the PC trips a breaker, disconnect it and get qualified help instead of resetting the breaker again. Burnt connectors or damaged plugs also end this check; do not power the system through them.

3. Make the machine safe before opening it

Turn the PSU off, unplug the mains cable and follow the manual's discharge instructions. Wait for standby indicators to go out before touching internal connections. Take a photo so you can put cables back where they belong. These steps allow inspection of the PC; they do not make the inside of a PSU safe to open. Leave that enclosure closed. If a cable's label or destination is unclear, identify it from the manual before trying it in a socket.

4. Trace the case power button

Find the front-panel header diagram in the motherboard manual. Trace the case's POWER SW cable to the pins shown there. It is easy to put the small plug onto an adjacent LED or reset pair, or shift it one pin sideways. Check the cable for trapping or damage and make sure the case button is not physically stuck. If the board has a documented onboard start button, that gives you a supported way to start it. Do not improvise a live screwdriver-bridging test.

5. Verify required motherboard and GPU power

Check the main motherboard connector, the CPU power sockets required by the board, and the graphics card's power connections. Modular PSUs need both ends of each cable checked. Keep CPU/EPS and PCIe cables in their intended roles; a similar-looking plug is not enough to establish compatibility. Use the exact PSU's supplied cables or explicitly approved replacements. Cables from another supply, even one from the same brand, can use different PSU-side wiring. Remove unverified extensions or adapters from the test setup.

6. Look for an assembly fault without forcing a restart

Look for an extra motherboard standoff, a loose screw, a pinched cable or an incorrectly seated connector. If the system starts briefly then stops, also check that the CPU cooler is fitted and connected before another attempt. Correct a specific fault, reassemble safely and try once. Taking every component out together may get the machine working by chance, but it also removes the clue to what was wrong. If there is scorching, liquid damage or a recurring shutdown you cannot explain, stop and arrange service.

7. Use a controlled replacement test

When the outlet, switch, POWER SW and required cables all check out, ask the PSU or motherboard maker for the next diagnostic step, or use a competent repair technician. A suitable known working PSU can help separate a power fault from the rest of the build. Its own approved modular cables must replace the original PSU's cables during that test. A paperclip test or a spinning PSU fan cannot establish reliable operation under the PC's load. Provide the parts list, connection photos and the checks already completed so support can move beyond the basics.

Your checklist

• Distinguish no startup from a PC that runs without a picture.
• Check the outlet, mains lead, power strip and PSU switch.
• Unplug mains power before inspecting the inside of the PC.
• Verify POWER SW and all required power connections against the manuals.
• Use a controlled PSU replacement test if needed, with that supply’s own approved cables.