Holy Moly -- Residual Electricity????

Is there some such concept as "residual electricity"???

There was a problem with a computer at work...it's a new Dell running
WinXP Pro...everything's fine, I go to lunch and come back to a blank
screen that won't wake up from power-save/sleep mode!! I do the
obvious and check connections, making sure they're secure and
whatnot. I turn off the computer and turn it back on a few times, to
no effect!

Tech Support suspects some kind of a "power management" issue --
whatever that is -- and suggests that I leave the system off for a few
minutes, literally, to let things "clear"...whatever that means. Sure
enough, however: it works!

So now I'm here asking, because Tech hasn't the time to puzzle over it
with me, WHAT HAPPENED??? And how come shutting off power for a few
seconds isn't comparable to leaving power off for a few
minutes????????????

TIA!

In sci.physics Prisoner at War wrote:

Is there some such concept as "residual electricity"???

There was a problem with a computer at work...it's a new Dell running
WinXP Pro...everything's fine, I go to lunch and come back to a blank
screen that won't wake up from power-save/sleep mode!! I do the
obvious and check connections, making sure they're secure and
whatnot. I turn off the computer and turn it back on a few times, to
no effect!

Tech Support suspects some kind of a "power management" issue --
whatever that is -- and suggests that I leave the system off for a few
minutes, literally, to let things "clear"...whatever that means. Sure
enough, however: it works!

So now I'm here asking, because Tech hasn't the time to puzzle over it
with me, WHAT HAPPENED??? And how come shutting off power for a few
seconds isn't comparable to leaving power off for a few
minutes????????????

TIA!

Capacitors.

--
Jim Pennino

Remove .spam.sux to reply.

wrote in message
news

Capacitors.



capacitors usually discharge when the current is switched off - their main
job is to smooth current, not to store volts....

When you turn it off and leave it off for a few minutes, it allows the
capacitors in the power supply to discharge.
With the power supply caps discharged, you in effect are guaranteeing a good
power on reset when you power on.
"Prisoner at War" wrote in message
oups.com...

Is there some such concept as "residual electricity"???

There was a problem with a computer at work...it's a new Dell running
WinXP Pro...everything's fine, I go to lunch and come back to a blank
screen that won't wake up from power-save/sleep mode!! I do the
obvious and check connections, making sure they're secure and
whatnot. I turn off the computer and turn it back on a few times, to
no effect!

Tech Support suspects some kind of a "power management" issue --
whatever that is -- and suggests that I leave the system off for a few
minutes, literally, to let things "clear"...whatever that means. Sure
enough, however: it works!

So now I'm here asking, because Tech hasn't the time to puzzle over it
with me, WHAT HAPPENED??? And how come shutting off power for a few
seconds isn't comparable to leaving power off for a few
minutes????????????

TIA!

They discharge, but it can take some time depending on the capacitors.
A few minutes is not at all unusual.

--
Jupiter Jones
http://www3.telus.net/dandemar
http://www.dts-l.org


"Gordon" wrote in message
...
capacitors usually discharge when the current is switched off -
their main job is to smooth current, not to store volts....

On Mon, 05 Nov 2007 20:52:31 GMT, "Unknown"
wrote:

When you turn it off and leave it off for a few minutes, it allows the
capacitors in the power supply to discharge.
With the power supply caps discharged, you in effect are guaranteeing a good
power on reset when you power on.


That is my understanding too of capacitors in general !!

Gordon wrote:
wrote in message
news
Capacitors.



capacitors usually discharge when the current is switched off - their main
job is to smooth current, not to store volts....



True, but they don't discharge instantaneously. Ever hear about the
"time constant" of an R-C circuit?

T = R × C
whe
T = time constant in seconds
R = resistance in ohms
C = capacitance in farads

The time constant is the time taken for the charging (or discharging)
current (I) to fall to 1/e of its initial value (Io).

After each time constant the current falls by 1/e (about 1/3). After 5
time constants (5RC) the current has fallen to less than 1% of its
initial value and we can reasonably say that the capacitor is fully
(dis)charged, but in fact the capacitor takes for ever to (dis)charge
fully!

--
Lem -- MS-MVP - Networking

To the moon and back with 4KB of RAM and 72KB of ROM.
http://en.wikipedia.org/wiki/Apollo_Guidance_Computer
http://history.nasa.gov/afj/compessay.htm

"Gordon" wrote in message
...
: wrote in message
: news :
: Capacitors.
:
:
:
: capacitors usually discharge when the current is switched off - their main
: job is to smooth current, not to store volts....

That shows how much you know -- which is zilch.

"Androcles" wrote in message
.uk...

"Gordon" wrote in message
...
: wrote in message
: news :
: Capacitors.
:
:
:
: capacitors usually discharge when the current is switched off - their
main
: job is to smooth current, not to store volts....

That shows how much you know -- which is zilch.




Well rooty toot to you.

On Mon, 5 Nov 2007 16:36:06 -0500, "Tom Lake"
wrote:



"Jupiter Jones" wrote in message
news:1xLXi.29858$XF6.22011@edtnps90...
They discharge, but it can take some time depending on the capacitors.
A few minutes is not at all unusual.

You can get some nasty burns from a TV that's unplugged due to those
things!

Tom Lake

Almost sounds like you speak from experience grin. I've unplugged
tv's but never had any ill effects from it luckily. Of course I don't
open it up either.