Power-Not-Good Signal


I have been having an issue with the rig I built back in June. Occasionally, usually when I first boot in the morning, nothing happens when I press the power button. I have found that cycling the power strip and power supply, disconnecting and reconnecting the cord, or slapping the side of the case fixes the problem. I have also had some rare instances where the computer unexpectedly shuts down, as if it were unplugged. Since this is a relatively new rig, most of the parts (with the exception of the motherboard, which I purchased as an open-box item) are still under warranty. I just need to know what component might be at fault—I suspect the power supply or the motherboard.

—Scott Odle

The Doctor concurs with your diagnosis that the power supply is the likely culprit. When you press the power button, the PSU turns on, does a diagnostic, and settles the voltage down to the point where it is safe to boot. Once that’s done, it sends a “power-good signal” to the motherboard, and the system boots. If the power-good signal is not sent, the board will not boot. If the power-good signal stops during operation, the system will shut down as though the plug has been pulled. So, that’s your first area to investigate. Since it’s under warranty, you’ll want to exchange the PSU. The fact that your motherboard was an open-box item is also a cause for concern, and it may very well be bad, which is why it got returned to the store in the first place. Your experience with a new PSU should answer that question.

SUBMIT YOUR QUESTION Are flames shooting out of the back of your rig? First, grab a fire extinguisher and douse the flames. Once the pyrotechnic display has fizzled, email the doctor at doctor@maximumpc.com for advice on how to solve your technological woes.

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