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Problem:

Power went out for about an hour yesterday morning. I didn't worry about it much because all my electronics are behind surge protectors, but when I tried to boot up my old PC this afternoon it didn't respond to the power button in any way. No lights, no fans, no sound, nothing. Checking inside the case, the interior power LED (which is normally solid green, even with the computer shut off) is flickering - not flashing, but going on and off fast enough to look like it's just dimmer than usual.

System specs:

  • PSU - Thermaltake Toughpower QFan 650W ATX 2.2
  • CPU - Intel Core i5-2500K, 3,3GHz, 6MB Cache
  • Motherboard - Asus P8P67 REV3.1
  • Memory - 16Gb Kingston KVR13N9S8K2/8 RAM 8 GB 1333 MHz DDR3
  • Graphics - MSI NVidia GTX 970 (4Gb)
  • Hard Drives - Two SSD, two regular. I can probably hunt out the specs if it's important.
  • Sound card - Asus Xonar

Things I have tried:

Plugged the computer directly into the wall, bypassing the surge protector. Disconnected all peripherals. Disconnected the power supply from everything and tested the main motherboard connection with a multimeter. All the pins seem to be within tolerances. Reseated the RAM. Replaced the CMOS battery. Checked the power and reset switches. Disconnected the graphics and sound cards.

e: To be clear, I shorted pins 15 and 16 on the psu (at which point it started up fine) and checked all the voltages with a multimeter. They all looked fine.

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    Have you tried with a different power supply? – DRP Jan 25 '18 at 20:10
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    When you mentioned "Checked the power" I assume this included testing your PSU? – Cheesus Crust Jan 25 '18 at 20:10
  • Yeah, I checked the PSU with a multimeter (added details to the post). I haven't tried a spare power supply yet, but I'll see if I can dig one out later. The fact I don't even get a PSU fan in response to the power button made me discount it as the cause, but I guess anything's worth a try at this point. – Simon Watson Jan 25 '18 at 20:17
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    You know how to start the power supply by shorting the pins in the PSU connector. Do that with the connector plugged into the motherboard. It's safe (so long as you short the correct 2 pins!). If it doesn't start, your motherboard is damaged. – I say Reinstate Monica Jan 25 '18 at 20:34
  • Not sure jamming bits of wire inside my computer with the power on on the authority of someone on the internet is the smartest thing I've ever done in my life, but you got an upvote so I'm sure it's fine :) It didn't start, so I guess that's the motherboard dead. Thanks for your help. – Simon Watson Jan 25 '18 at 22:02
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If you do not have a spare power supply, your best bet is to test your current one with an ATX PSU tester or take it to a local computer shop to be tested. For future reference it is helpful to keep a spare PSU or ATX tester on hand. If your PSU turns out to be fine check to see if the motherboard POSTs successfully I.e. CMOS reports manufacturer logo or BIOS version etc. Next Test your RAM a single stick at a time(refer to your motherboard manual for preferred RAM slot arrangements). Use MemTest or through a bootable Linux envrioment on a USB flash drive.

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