Member Avatar for phobos

I’m at a loss...I built a system that functions perfectly. Except...when it is powered down it automatically reboots in about 3 minutes. I've seen this with win 2000, but this system has XP pro + all updates. It's a complete new build. No recycled parts. In the bios power management is enabled, but all the options are disabled. The bios is the latest and greatest...so...I'm lost...

PC Chips M916 mobo
P4 2.4
480W power sup
1GB PC3200


Any ideas???

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  • Latest Post Latest Post by jwenting

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A short, practical checklist to supplement the replies from , and . The usual causes are an enabled wake source (network, keyboard, USB, RTC/alarm), a flaky front-panel or PSU behaviour, or a BIOS option that restores power. The next steps isolate those possibilities in under an hour.

Start with a minimal-hardware test. Unplug the Ethernet cable and remove all USB devices (keyboard and mouse included) before shutting down. If the system stays off, plug devices back one at a time to find the offender. If it still reboots, remove the case power switch connector from the motherboard and, after unplugging the mains, use the short-power-header method in the manual to power it on — this rules out a sticky or shorting front-panel switch (do not probe while the PSU is connected).

Check BIOS and OS power settings next. Look for and disable settings named like Wake on LAN, Power On by PCI/PCI-E, Wake on USB, RTC/Resume by Alarm, or Restore on AC Power Loss. In Windows Device Manager, open the NIC, keyboard and mouse properties and uncheck any "allow this device to wake the computer" options; in NIC advanced settings disable pattern-match/magic-packet wake options. Examine Task Scheduler for tasks allowed to wake the machine and clear any wake timers. Review the System event log timestamps around the unexpected boot for clues.

If the problem persists, try clearing CMOS (reset BIOS to defaults) and test with a known-good PSU on the bench with only CPU, one RAM stick and power to the board. If swapping the PSU or booting barebones stops the unwanted restart, the PSU or a peripheral card is the likely cause. If BIOS changes made things worse, consider restoring/rolling-back a BIOS version (flash with care). Safety note: always unplug mains before touching front-panel headers or swapping the PSU.

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Member Avatar for jbennet

My pc. has a similar problem. Whenever I turn on my hi - fi it shuts down or turns itself on.

Member Avatar for DMR

Hi phobos- welcome to TechTalk. :)

This may be a long shot, but the "wake on lan" (WOL) networking feature sometimes causes this behaviour.

If you haven't done so already, disable WOL in the BIOS, and uncheck the "Allow this device to bring the computer out of standby" option in the Power Management tab of your network card's Properties window.

Member Avatar for jwenting

Wake on keyboard also can do it. Some keyboards aren't properly grounded and can send small random signals even when no key is pressed. This is usually no problem as they get filtered out in the keyboard processor but the wakeup system might trigger on them.

Of course a sure way to turn it off is to literally pull the plug :)

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