Member Avatar for mmszyman

I normally leave my computer on, but one day I came home and noticed it was off. I went to turn it back on and nothing happens at all. No sounds, no nothing. The power light in the back off the desktop is on though. So I have zero idea what could be wrong with it.

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Short expert summary and next steps (builds on comments from , , and )

The rear power LED usually means the PSU is getting AC and its standby rail (+5VSB) is alive — it does not mean the main +12/+5/+3.3 rails have come up. That narrows the fault to the start signal/cabling, a PSU that won’t spin under load, or a motherboard/front-panel wiring problem. (en.wikipedia.org)

Practical, safe checklist to narrow it down (do these in order)

  • Confirm the wall outlet, power cord and the PSU’s on/off switch (swap the cord or outlet if available).
  • With the PC plugged in but powered off, check +5VSB on the 24-pin connector (purple wire, pin 9) using a multimeter or an inexpensive PSU tester — this tells you if standby power is present. If +5VSB is missing, the PSU is likely faulty. (lifewire.com)
  • If +5VSB is present, short the motherboard power-switch pins briefly (PWR_SW on the front-panel header) to simulate the case button. If that starts the machine, the case switch or wiring is the problem. (techwalla.com)

How to isolate the PSU vs motherboard safely

  • If the board does not start when you short PWR_SW, use the accepted “jumper/paperclip” method on the PSU 24-pin (green PS_ON to any black ground) to see if the PSU will run on its own. Some modern PSUs have semi-passive fans and won’t spin unless loaded — a spinning fan is useful but not definitive. Use caution and avoid touching exposed pins. (support.nzxt.com)

When to replace or call a pro

  • If the PSU fails the tester/multimeter or paperclip check, replace it or swap a known-good unit before blaming the motherboard. Do not open a PSU (dangerous capacitors); if you see burning smell, bulging caps, or visible damage, replace the unit or get professional service. (tomshardware.com)

These steps let you test cheaply and safely before buying parts. If a known-good PSU still won’t start the board after the PWR_SW jump, focus on the motherboard (shorts, damaged caps) or the front-panel wiring.

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Member Avatar for Suspishio

There are two possibilities here:
1/
The computer's PSU gave out - it is no more

2/
A power glitch zapped something.

If you're lucky, it's a fuse (if the PSU has one); if you're less lucky, a new PSU might do it, but there could be collateral damage on your mobo or RAM.

If the fans don't come on and the disk doesn't spin then unless the power switch is the problem (why should it be), I suspect the PSYU.

Member Avatar for cguan_77

try disconnecting the psu from the pc line for about 3 mins. then put it back and power it on, check if it will work. if it doesn't then try what Suspishio suggested..

Member Avatar for galanshi

Do you have a surge protector??
Probably an electric surge fried up your PSU.
It is a cheap easy replacement, google power supply. 400 watts should be enough. And get your self a surge protector if your gonna leave ur pc on constantly.
Hope it did't get to your mother board

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