Member Avatar for Buppy

Hi,

Recently I started to encounter a new issue with my 3 year old PC. It sometimes turns off randomly, then turns back on after a few seconds. It can happen anytime, even when OS has not booted yet. Sometimes it turns off and on repeatedly, like struggling to keep powered on. Overheating should not be the issue because it has happened right after I turn ir on for the first time that day. Nothing new has been added or installed recently. Also not overclocked.

Could it be a faulty PSU or other hardware?

Thanks

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  • Latest Post Latest Post by rproffitt

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described intermittent immediate shutdowns (sometimes repeating) even before the OS loads. That pattern most often narrows the field to: failing PSU or its rails, failing electrolytic capacitors/VRMs on the motherboard (or GPU), a short or bad front‑panel/power switch, or BIOS/power‑management oddities. 's instinct about aged PSUs and caps is a common and sensible place to start.

Practical, ordered checks to isolate the fault:

  • Power off and unplug. Visually inspect motherboard and PSU (visible caps) for bulging, leaking, or brown residue. Any obvious damage is significant.
  • Try a minimal bench boot: motherboard + CPU + single RAM stick + PSU + video (onboard or single GPU) and monitor. If stable, add drives/cards back one at a time to find the offender.
  • Swap the PSU with a known‑good unit or use a proper PSU tester. The common "paperclip" trick only proves the fan spins and won’t reveal rail instability under load.
  • Disconnect front‑panel connectors and briefly short the motherboard power‑on pins (per the manual) to rule out a faulty case switch.
  • Reset BIOS to defaults and check/disable unusual wake/resume options. If the OS sometimes boots, check Event Viewer (Kernel‑Power events) and any memory dump files for clues.

Interpretation and next moves: a good outcome after a PSU swap points to the power supply. Persistent cycling on a minimal build implicates the motherboard (VRM, solder joints, or caps) or rarely the CPU. If bulging caps are present, replacement of the board or professional cap replacement is warranted. If there’s burning smell, heat, or visible damage, cut power and avoid further testing.

Safety and logistics: discharge capacitors, ground against ESD, and only perform live tests if comfortable with mains safety. For definitive results, a bench test with a known‑good PSU and documented voltages/beep codes will narrow the cause quickly.

Member Avatar for rproffitt

Sure. When it does come up, look in the bios for a power resume on loss mode. Turn that off. Such a PC has priors and tracked to heat, PSU, motherboard and other parts. The first time of the day points me more to the old BAD CAPS PLAGUE (see google) or a PSU that was barely big enough in the first place. PSUs lose capacity over time so new PC techs often must learn about that.

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