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I am not sure if they are the same, but something puzzling just happened. My dell precision workstation 2007 has been fine ever since, with many, many power outages over the years. But there is a time a guy pulled the power cable off, and a few days later the PC no longer boot, with loud whooss fan sound at startup. After testing, everything was fine, only the motherboard died, with apparent fried capacitors.

Can anyone please explain? Thank you.

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  • Even power outages could be very different (no voltage, low voltage, wrong frequency, …).
    – Daniel B
    Commented Oct 21, 2020 at 5:52
  • If the PC died "a few days later", the cable being pulled out was not the cause. The motherboard was dying for months already.
    – Michael Harvey
    Commented Oct 21, 2020 at 8:37
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    This might be more suited to electronics.stackexchange.com because it's more of a theoretical question about electronics than a computing problem
    – James P
    Commented Oct 21, 2020 at 9:12
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    "... and a few days later ..." -- Seem like you insist on making a connection between events days apart rather than assume a coincidence. "After testing, everything was fine, ... with apparent fried capacitors." -- What kind of "testing" and by whom?
    – sawdust
    Commented Oct 21, 2020 at 10:27

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Cutting off power to PC can not damage the hardware. Only OS can be messed up, and unsaved data can be lost. The motherboard died for some other reason, and it would happen even if power cable was not unplugged.

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  • This is only partially true. For example if the disconnection was not a clean break (think rapidly turning off and on and off again) it could have caused the components to draw more power then they otherwise would and it could be the straw that broke the camels back.
    – davidgo
    Commented Oct 21, 2020 at 8:43
  • @davidgo Yes that would be problematic, but that is not what the OP descried. While PC is powering on capacitors are being charged from 0 charge and electric current is much higher than.
    – Zoran Jankov
    Commented Oct 21, 2020 at 9:19
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@Zoran Jankov what if the power supply is very old like this one since 2007?

I have a theory. Even assuming the power supply is new and everything is functioning as expected from an international standard point of view, it might be still different if one unplugs the power cable from the PSU directly instead of from the wall outlet; there would be no different between unplugging the cable from the wall outlet and electricity outage because the current flowing/voltage is the same, unlike unplugging directly from the PSU where the current/voltage is halted immediately. And since the PSU is very old, its surge protection might not hold- result in short circuit? Possible?

#Daniel B exactly if you think in terms of micro nano level

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    Whether you pull the connector out of the PSU, or the connector at the wall socket, or even chop the cable in the middle with an axe, the result is exactly the same. The AC power stops.
    – Michael Harvey
    Commented Oct 21, 2020 at 8:30
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    @MichaelHarvey: I'm no expert but I don't agree. By pulling out the cord you are physically disconnecting live and neutral and removing any direct grounding - I don't see how that could happen during a typical power cut. I would expect this could affect how some of the capacitors discharge. Maybe if it was disconnected at the AC peak and the capacitors were left charged this would put extra strain on them, I really don't know but clearly it's complicated
    – James P
    Commented Oct 21, 2020 at 9:08
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    I was disagreeing with simonv's assertion that it might make a difference whether the connector at the PSU end of the power lead was yanked out, or the one at the wall outlet. Regarding "grounding" in the electrical safety sense, removal of this from a PSU would have ne effect whatsoever on what happens to capacitors on the motherboard, which only "see" DC supplied by the PSU.
    – Michael Harvey
    Commented Oct 21, 2020 at 9:15
  • @MichaelHarvey: Yes I was thinking more about it potentially damaging the PSU than the motherboard but it sounds like that wasn't the case here. Whether or not disconnecting it like that could somehow translate to a surge on the DC output I don't know
    – James P
    Commented Oct 21, 2020 at 9:23
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    @simonv -- Please take the Tour and learn how to use these sites. This is not a forum for a discussion.
    – sawdust
    Commented Oct 21, 2020 at 10:30

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