Troubleshooting
An ordered list of causes from most to least common. In most cases the problem is in the first three entries.
Step 1 of 3
Check the switch on the back of the PSU — a surprisingly common cause, and worth ruling out first.
Check the power button cable on the front panel pin block. On the wrong pair of pins it does nothing. To rule out the button itself, briefly bridge the two PWR_SW pins with a screwdriver.
Check that the 8-pin EPS cable near the CPU is connected. Without it many boards give no reaction at all, including no LEDs.
Step 2 of 3
First check the monitor is connected to the graphics card and not the motherboard. That accounts for most reports of this symptom.
Remove the memory and refit it firmly until the clips click. Then try starting with a single module in the second slot from the CPU. Badly seated memory is the second most common cause.
Check the diagnostic LEDs on the motherboard. Most modern boards have four, marked CPU, DRAM, VGA and BOOT — the lit one shows where startup stopped, which saves a lot of guessing.
Step 3 of 3
A short loop, two to three seconds at a time, usually points at the memory or its profile. Clear the BIOS and start with EXPO or XMP disabled.
If the loop only appears under load, suspect an underpowered PSU or a poorly seated graphics card power cable.
Also check that the CPU cooler is evenly tightened. A block tilted to one side causes immediate overheating and a protective shutdown.
A complete walkthrough from unboxing to first boot. Order matters — the sequence here saves a lot of backtracking.
What to do once the case is closed: the memory profile, boot order, and the settings genuinely worth changing.
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