My HP E9280F desktop was working normally, but after sitting overnight it had no image on the monitor even though the PC appeared to be running. Holding the power button did nothing, and after unplugging it, removing and reseating the RAM and graphics card, cleaning the contacts, and removing the CMOS battery briefly, the problem remained. The keyboard and mouse also receive no power. The RAM was replaced in 2023, while the CMOS battery is original and the Cooler Master 1000W power supply dates back to 2012. Now the computer starts as soon as I connect the PSU cable, without pressing the power button. What could cause this, and what should I test next?
2 Answers
If the BIOS is not configured to power on after AC is restored, the behavior could point to a failing motherboard, an aging power supply, or a shorted power-button circuit. Reseat the main 24-pin motherboard connector and the CPU power connector. You can also disconnect the case’s front-panel power-switch cable and briefly short the two power-switch pins with a screwdriver to test whether the button or its wiring is stuck. Given that the PSU is from 2012, testing with a known-good replacement would also be a strong next step.
Some BIOS settings can make a computer start automatically when AC power is connected. Look for an option named something like “Restore AC Power,” “AC Power Loss,” or “Wake on AC,” and set it to “Off” rather than “On” or “Last State.” However, that setting wouldn’t explain the missing display and dead USB ports by itself.
Could that setting still be involved if I get no display at all and can’t access the BIOS?