Powercuts...

meghatronic · 11 Oct 2006 at 10:06

I don't understand something.

We just had lightning strike somewhere and the power in the entire area went out for 3-5 secs. Our alarm went off, even the phones powered down - as did the tv and freeview box.

I came up upstairs to check the pc and it is fine.... :s Why didn't it power off/restart? It was happily chugging away burning a dvd.

Any ideas why? Does my pc have its own renewable power source that I could exploit to take over the world? Everything else in the house turned off/restarted.

Answers on a postcard.

Corasik · 11 Oct 2006 at 10:40

Sometimes this will happen if you have a good powerfull PSU, and the computer isnt doing much, the main smoothing caps can actually hold enough charge to keep the PC running for a short time. 3-5 seconds seems a bit much, but quite often my PC keeps running during those brief power flicks.

Jez · 11 Oct 2006 at 10:52

At a guess i'd say that you are overestimating how long it went off for. As said the smoothing caps in a decent PSU will hold enough charge to overcome a 1 second or so brownout.

I get them all the time living right out in the country and it lasts through the little flickers, although i have now resorted to using a UPS as that will keep it going through the slightly longer ones.

Pinkeyes · 11 Oct 2006 at 11:08

Where do you live ?

Exactly the same thing happened to us (near Manchester) - but my PC is on a UPS, so I didn't notice.

Looked out of the windows and the electric in the buildings across campus had gone off.

Jez · 11 Oct 2006 at 11:10

Does your UPS not go crazy when the AC is removed? All of mine (i have about 6-8 different ones) bleep at me like mad.

shine · 11 Oct 2006 at 11:16

Jez said:
Does your UPS not go crazy when the AC is removed? All of mine (i have about 6-8 different ones) bleep at me like mad.

Mine only goes crazy after its been on battery for about 20 seconds or so.

Captain Fizz · 11 Oct 2006 at 11:22

Your PSU has large caps.

That happened to me - All of the PC's in the house turned off except mine.
(Preceeded by a large bolt of lightning)

I had a 550W PSU wich was bigger than the other PC's and the caps provided the power it needed.
The PSU then preceeded to eat HDD's whilst in soft-off.

(300GB went ta-ta)

But the PC itself kept running during the actual outage.

meghatronic · 11 Oct 2006 at 11:22

Near Manchester actually (Bolton).

It was long enough for me to look out the window and see the alarms all going off... so I'd say more than 1 second.

I guess that is why you pay £70 odd for a psu...

Enermax (Liberty 500W or 550W I forget) I'm impressed!

stoofa · 11 Oct 2006 at 12:51

A long time ago, when I was still selling PC's through a showroom for a living (and these were 486's and early Pentium) one month our PC's started to ship with a new feature.
The power supply could cope with minor blackout's.
Basically as long as the power outage was around 1-2 seconds in length only then the chances were your PC would remain up & running.
This was an amazing little feature as up until then the slightest power outage and off the PC went.
This feature became standard (couldn't tell you the technology behind it, but probably just the sizr of the caps) and I think most PSU's these days can cope with such a short drop.

I personally use a UPS which powers my PC, LCD and firewall/router - but that is there for those >3-4 second outages.