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When calling support the other day he told me to reset my DSL modem by pulling out the power, leave it out for 10 seconds, and then plug it back in. This is something I have heard many times with different kinds of equipment. I have also heard it in relation to computers. That when you turn it off, you should wait at least 10 seconds before you turn it on again.

  • Why not just plug it in again right away?
  • Why 10 seconds, instead of, say... 3 or 30?
  • Should you really, always do this; just with certain types of equipment; just in certain circumstances; or is it just a "myth" thing that people have said so often that they believe it to be fact?
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+1 for a very nicely written question :) – Phoshi Dec 19 '09 at 11:36
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5 Answers

up vote 33 down vote accepted

A lot of modern technology contains capacitors! These are like energy buckets, little batteries that fill up when you put a current through them, and discharge otherwise. 10 seconds is the time it takes most capacitors to discharge enough for the electronics they're powering to stop working. That's why when you turn your PC off at the wall, things like an LED on your motherboard take a few seconds to disappear. You probably could wait a different time, but 10 seconds is the shortest time you can be sure everything's discharged.

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This would have been my answer if I was fast enough! – DaveParillo Dec 19 '09 at 11:37
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+1 for enlightening me! – Ivo Flipse♦ Dec 19 '09 at 11:37
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Couldn't have put it better. – ChrisF Dec 19 '09 at 11:41
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if you have the soldering iron what do you need the wire cutters for? – quack quixote Dec 19 '09 at 15:28
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I'd guess this does much the same thing - plus holding down the button makes sure you spend a bit of time waiting! – Phoshi Dec 23 '09 at 16:05
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up vote 4 down vote

In my experience 0 seconds work just as well as 10 for restarting the equipment.

The reason in my opinion for the 10 seconds is only to ensure that the client has totally pulled the plug out of the socket. Some people just don't pull it out all the way unless they have to wait for X seconds with it in their hands.

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More social engineering: A help desk Bob will tell you to reverse your ethernet cable. It's much more reliable than taking the user's word that it is, in fact, plugged in. :) – Richard Hoskins Dec 19 '09 at 17:49
Reverse your ethernet cable... hehe, that's brilliant :p – Svish Dec 19 '09 at 21:01
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up vote 3 down vote

Phoshi said well, but there could be another reason for that, a very less technical one: it is kind of related to social engineering.

The majority of customer care call center hires just...everyone! And there you could find someone that understand what you're asking, as well as someone who don't understand/don't care about, and the usual solution for every problem is (in the latter case) something like "Reboot" or "unplug and replug"! :D

Sadly, I saw that with my own eyes...

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Often a reboot does work though. – TylerF Dec 19 '09 at 19:12
No doubt on that! – dag729 Dec 19 '09 at 20:42
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I hate it when I have to explain things to the support guy... I mean, I am calling them for help. And I often find myself having to help them figure out the problem I am having. Very annoying! – Svish Dec 19 '09 at 21:03
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up vote 2 down vote

To be certain that all capacitors have, in fact, discharged, you may also cycle the power button while the power is disconnected. All this does is provide a reliable path for the discharge and, because some capacitors discharge their energy more slowly than others, this proceedure insures it has been done.

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Not typically required, but could help. Some larger caps in some circuits can hold charges for days or even weeks. – Brian Knoblauch Dec 21 '09 at 13:25
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up vote -1 down vote

Whatever you do, don't try to pull the plug from a running computer (unless it has frozen to the extent that Alt + Ctrl + Del won't work). This can seriously damage the operating system or corrupt the file system leading to loss of data.

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Even in such a situation, I've always assumed holding the power button might let the mobo try and protect itself a little. – Phoshi Dec 21 '09 at 11:40
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