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Power supply turning on pc for 1 second when off?

Got a strange one for you all. Stumped me aswell so hopefully someone can help out. Took wires out of back of pc to move it to the other side of the desk. Flipped the wall switch and the PSU switch to off just to be on the safe side. Plugged everything back in and flipped the wall switch but left the PSU switch to off. Didn’t realise and pressed the on button on the case and the PC tried to power on and turned off straight away. Obviously wouldn’t boot because the power supply is off but why would it even try to boot with it off? Flipped the PSU switch to on and all booted fine. Strange one any ideas ?


Ryzen 5 3600
750watt Corsair platinum psu 
16gb ddr4 ram 
Gigabyte b550i

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there is left over current inside the PSU. Think of it this way, when you disconnect your monitor from AC power, the LED to show it has power will remain on till the left over power is consumed. 


I have had the same thing with my pc as well, its normal. It will only do it once. If you try again you will see that nothing will happen, assuming PSU is still off.

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The capacitors in a power supply can hold a charge, enough for the computer to "start" briefly. A 750W PSU can hold a fairly large charge even when unplugged. It'll likely just flash some lights and maybe start spinning a fan for half a second and then just switch off again.

CPU: Intel i7 6700k  | Motherboard: Gigabyte Z170x Gaming 5 | RAM: 2x16GB 3000MHz Corsair Vengeance LPX | GPU: Gigabyte Aorus GTX 1080ti | PSU: Corsair RM750x (2018) | Case: BeQuiet SilentBase 800 | Cooler: Corsair H100i AIO | SSD: Samsung 970 Evo 500GB + Samsung 840 500GB + Crucial MX500 2TB | HDD: Seagate Ironwolf 8TB + 2x Seagate Ironwolf 6TB | Monitor: Acer Predator XB271HU + Samsung BX2450

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