Most first-build problems come down to something not plugged in, not fully seated, or plugged into the wrong place. Start with what you can see happening and work down the list. Change one thing at a time, so you know what fixed it.
When it won’t turn on
- Check that the switch on the back of the power supply is set to I and that the wall socket or power strip works.
- Check that the 24-pin motherboard cable and the 8-pin CPU (EPS) cable are pushed all the way in. The CPU cable is near the top-left of the board, and some boards have two.
- Check the case’s power-switch lead is on the right two front-panel pins. The motherboard manual has the pin map. To rule the lead out, briefly touch the two power-switch pins together with a screwdriver tip; if the PC starts, the case button or its lead is the problem.
- Unplug the PC, hold the case power button for 30 seconds to drain leftover charge, plug it back in and try again.
Fans spin, but no display
- Wait. On the first boot with DDR5, memory training can keep the screen black for a minute or more.
- Plug the monitor cable into the graphics card, not the motherboard. (Motherboard outputs only work with a CPU that has integrated graphics, and many boards turn them off when a card is installed.)
- Check the graphics card’s power cables are fully seated. A 12V-2×6 (16-pin) connector should sit flush, with no gap.
- Read the motherboard’s debug LEDs (CPU, DRAM, VGA, BOOT) or its two-digit code display, if it has one. The light that stays on points to the part that failed; the manual explains the codes.
- Try another cable or monitor input. A monitor set to the wrong input looks exactly like a PC that won’t display.
RAM not detected
- DDR5 needs firm pressure to seat. Take the sticks out and push them back in until the latches on both ends click.
- Use the slots the manual marks for two sticks, usually A2 and B2 (the second and fourth from the CPU).
- Try one stick on its own in A2. If it boots, try the other stick, to find out whether one stick or one slot is at fault.
- A newer memory kit may need a BIOS update to train properly. Check the board’s memory support list (QVL) for your kit.
Still stuck: strip it down
Disconnect everything the PC doesn’t need to reach the BIOS: keep the CPU, cooler, one memory stick and the graphics card, and unplug drives, extra fans and USB devices. If that boots, add parts back one at a time. If it doesn’t, rebuild outside the case on the motherboard box, which rules out a short against the case (for example a stray standoff behind the board).
It boots, but crashes or freezes
- Load BIOS defaults first. If the crashes stop, a memory profile or overclock was the cause; try the kit’s slower profile.
- Test the memory. Run MemTest86 from a USB stick overnight. Any errors mean a bad stick, a bad slot or an unstable speed.
- Watch temperatures. Use HWiNFO while gaming. A CPU pinned at its limit in light use, or a graphics card hotter than normal, points to a cooling or airflow problem.
- Check the power. Crashes only under heavy gaming load often trace to the power supply or to graphics card cables. Use the PSU maker’s own cables, one cable per 8-pin socket where possible, and a fully seated 12V-2×6 connector.
- Read Windows’ logs. Event Viewer’s “System” log and the Reliability Monitor (search for “reliability history”) show which component or driver failed around the time of each crash.
Recovering from a bad setting or BIOS update
If the PC stopped booting after you changed a BIOS setting, clear the CMOS to go back to the defaults. If a BIOS update failed, many boards can re-flash from a USB stick using the BIOS Flashback button, even when the board won’t start. The board’s manual explains how.
Still no luck? Post your parts list and what happens when you press power in the forum’s Troubleshooting board.