# Lights go out, computer comes powering on **URL:** \ **Category:** Factual Questions\ **Created:** [November 11, 2014, 2:26am UTC](https://boards.straightdope.com/t/lights-go-out-computer-comes-powering-on/704300 "2014-11-11T02:26:59Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Mr.Kobayashi](https://avatars.discourse-cdn.com/v4/letter/m/4af34b/32.png) [@Mr.Kobayashi](https://boards.straightdope.com/u/Mr.Kobayashi)\ **Post date:** [November 11, 2014, 2:26am UTC](https://boards.straightdope.com/t/lights-go-out-computer-comes-powering-on/704300/1 "2014-11-11T02:26:59Z")
A missed hit for the Style Council but a mystery to me, maybe you can solve it. Two plug sockets, opposite sides of a room. In one is plugged a lamp, in the other the desktop PC and her monitor via an extension. Shut down the compy, turn on the light, so far so normal…then turn out the light and, like clockwork…the fans and POST beep of the compy follow. But…how…? Surely this shouldn’t be possible. Do I have a mischievous poltergeist or something? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [November 11, 2014, 2:28am UTC](https://boards.straightdope.com/t/lights-go-out-computer-comes-powering-on/704300/2 "2014-11-11T02:28:57Z")
Inductive “kick” coupling to the PC power supply. What type of lamp is it? ---
**Author:** ![Mr.Kobayashi](https://avatars.discourse-cdn.com/v4/letter/m/4af34b/32.png) [@Mr.Kobayashi](https://boards.straightdope.com/u/Mr.Kobayashi)\ **Post date:** [November 11, 2014, 2:35am UTC](https://boards.straightdope.com/t/lights-go-out-computer-comes-powering-on/704300/3 "2014-11-11T02:35:33Z")
> [@beowulff](#): > > Inductive “kick” coupling to the PC power supply. > What type of lamp is it? Just your bog-standard standing lamp, looks a bit like [this](http://www.finsdesiecles-artdeco.com/13719-8689-thickbox/standing-lamp-art-deco-italy.jpg) (because that’s how I roll). Turn it off via the mains switch, the compy is powered down normally then…back on she goes just like I’ve switched it on. That doesn’t sound like it’d be particularly healthy for the PSU…since I noticed the pattern I’ve unplugged her from the socket before lamp usage and am saying several Hail Marys, also got some Holy Water on order. ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [November 11, 2014, 4:01am UTC](https://boards.straightdope.com/t/lights-go-out-computer-comes-powering-on/704300/4 "2014-11-11T04:01:11Z")
In the computer BIOS, there is usually a setting that says “Power on after AC power loss?” or something similar, that causes the computer to switch back on when it thinks it’s lost power. Could the lamp be triggering that? You can try toggling that option to see if it makes a difference. With most computers, you enter the BIOS (or its modern equivalent the EFI) by repeatedly pushing one of the following keys at boot: Del, F12, F11, F1. A message should briefly flash on screen telling you which key to push to enter setup. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [November 11, 2014, 5:09am UTC](https://boards.straightdope.com/t/lights-go-out-computer-comes-powering-on/704300/5 "2014-11-11T05:09:06Z")
> [@Mr.Kobayashi](#): > > That doesn’t sound like it’d be particularly healthy for the PSU… It’s not too bad, really. But you could avoid it by getting a power-conditioning unit (like a UPS) to plug it into. Probably a good idea, unless the power supply in your locality is better than most of the world. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [November 11, 2014, 5:44am UTC](https://boards.straightdope.com/t/lights-go-out-computer-comes-powering-on/704300/6 "2014-11-11T05:44:11Z")
By chance, does the lamp have a CFL or (I’m guessing) an LED light bulb in it? As others are saying, and I’m agreeing, I’m guessing that the computer thinks it’s briefly losing power, but I’ve noticed that some light bulbs, specifically dimmable LEDs, seem to put some feedback into the line. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 11, 2014, 10:06pm UTC](https://boards.straightdope.com/t/lights-go-out-computer-comes-powering-on/704300/7 "2014-11-11T22:06:37Z")
Weird post timing. I’ve started noticing something like this with my PC. But the trigger is me turning on my bedside lamp- it uses a classic touch switch bulb base. They are on opposite sides of the room but presumably same circuit.