MessageView 421F schematic

w_tom wrote:

Rather scary that so many know so much as to reply ...
without first learning electrical basics.
Click to expand...
Oh, gawd. He's invaded yet another group.
 
On Fri, 10 Jun 2005 21:39:09 -0000, howardkinsd@yaEXPUNGEhoo.com
(Howard Knight) wrote:

<snipped rec.audio as irrelevant>
I live in an older house that is not grounded. The ground prong on
the outlets isn't connected to ground or anything else. Also, I've
determined that the coax cable coming in to my cable modem is
grounded. Somthing seems to be making the ground prong on my outlet
hot. I've narrowed down the problem to my power strip. I've
unplugged everything from my outlet and I check the outlet for
voltage. Neutral to hot gives me 110V. Neutral to ground give me
nothing (actually, for some odd reason, there does seem to be a
slight voltage (less than 2V). Hot to ground also gives me nothing.
As one would expect.
Click to expand...
You say your outlet has no ground, but then you say you measure
voltage to ground. What are you using as the return reference for the
measurements? Please think about this question carefully, and what
the answer implies. Do you understand that electrical charge must
have a complete path in order for electrical measurements to become
useful? To understand your predicament, you should be somewhat aware
of how such paths are formed.

As others have mentioned, the outlet strips have internal circuitry.
This internal circuitry, the MOV's (metal oxide varistors), carry
minuscule currents when normal power is applied between hot and
neutral. The strips are designed to carry large transients away from
both the hot and neutral circuits to ground. Having an open and
unreferenced ground pin gives you access to the midpoint of a balanced
voltage divider between hot and neutral, so it is natural and expected
for you to read the 60V on the ground pin.

Given this information, you can conclude that you have set your
computer case to the midpoint of this voltage divider by plugging it
in to the unreferenced (also known as "floating") pin of your power
strip. Thus, when you insert yourself as a conductor between your
computer case and the cable shield that is grounded to earth at the
cable entrance to the house, you can expect to feel that 60V potential
difference. The neutral line will be earth grounded (possibly at the
entrance of the AC power into the house), and very close to the same
potential as the cable shield.

There are other interesting and complex consequences to your plan to
short the computer case to a water pipe. You need to hire an
electrician to get this straightened out, just as you might consult a
doctor about an injury or a lawyer about legal issues.
 
On Fri, 10 Jun 2005 23:51:39 -0500, Jim Adney <jadney@vwtype3.org>
wrote:

It's rather clear that no one before Gary had
much of a clue as to what was really going on here...

You can leave things just the way they are....
Click to expand...
Speaking of clues: if the OP leaves things "just the way they are," he
will have an ever-present and very real 60V potential between his
computer case and the cable shield. That's 60Vrms at 60Hz between
bare, exposed metal conductors possibly just inches apart. Dunno
about you, but I wouldn't want that.
 
On Sat, 11 Jun 2005 12:31:18 -0700, Al Brenan <nannerbac@yahoo.com>
wrote:


It's rather clear that no one before Gary had
much of a clue as to what was really going on here...
You can leave things just the way they are....

Speaking of clues: if the OP leaves things "just the way they are,"
he will have an ever-present and very real 60V potential between his
computer case and the cable shield. That's 60Vrms at 60Hz between
bare, exposed metal conductors possibly just inches apart. Dunno
about you, but I wouldn't want that.
Click to expand...

http://users.tkk.fi/~then/mytexts/ungrounded_pc.html
 
On Fri, 10 Jun 2005 23:31:57 -0000, howardkinsd@yaEXPUNGEhoo.com
(Howard Knight) wrote:

Todd H. (bmiawmb@toddh.net) wrote:
: ...your outlet is heinously miswired.

Not miswired, just wired 40+ years ago with no ground. Couldn't I
just ground the outlet myself? Run a wire from the ground in the
outlet to a water pipe outside? Would that solve my problems?

Howard
If you have a un-grounded U-Ground outlet installed in a 2 wire
Click to expand...
UN-GROUNDED box, this is a violation of most US electrical codes.
You need to replace 2 prong outlets wit 2 prong outlets UNLESS there
is a ground wire attached to the 1)box, 2)the green terminal on the
outlet.

Many bathroom outlet and light fixture boxes were required to have a
separate (bare) ground wire connected to the cold water piping. This
is fine until the addition of Di-electric union or plastic piping from
the water supply. If your electric service does not have a ground rod
driven into the earth, have this added to the required cold water
ground bond wire at the service entrance.

, _
, | \ MKA: Steve Urbach
, | )erek No JUNK in my email please
, ____|_/ragonsclaw dragonsclawJUNK@JUNKmindspring.com
, / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org
 
On Sat, 11 Jun 2005 02:43:59 -0400, w_tom <w_tom1@hotmail.com> wrote:

The wall receptacle safety ground must have a dedicated wire
connection to breaker box safety ground. Not to earth; to
safety ground. And definitely not a connection to pipes.
MODERN rules. Old rules DID require COLD WATER PIPES, but *never* GAS
Click to expand...
pipes.

, _
, | \ MKA: Steve Urbach
, | )erek No JUNK in my email please
, ____|_/ragonsclaw dragonsclawJUNK@JUNKmindspring.com
, / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org
 
Vidar Lřkken wrote:

Bullshit. The potential at the case is power leaked in the psu, not
_any_ other parts in the computer. The psu has a filter on the input,
which leaks tiny currents to ground/chassis. This has nothing to do with
the cpu or any other thing. It has nothing to do with induction afaik.
Click to expand...

Just for fun I measured those values on a atx psu connected to a 100W
load, trough a insulation xfmr. I measured 60-65V, and 70ľA. This
current is so tiny you won't normally feel it, so no danger to human
beings. However, if some equipment is earthed, and some not, it might
destroy electronics.
Also note that this was in a 220V IT circuit, which means that earth is
nominally floating.

--
MVH,
Vidar

www.bitsex.net
 
Vidar Lřkken wrote:
Vidar Lřkken wrote:

Bullshit. The potential at the case is power leaked in the psu, not
_any_ other parts in the computer. The psu has a filter on the input,
which leaks tiny currents to ground/chassis. This has nothing to do
with the cpu or any other thing. It has nothing to do with induction
afaik.




Just for fun I measured those values on a atx psu connected to a 100W
load, trough a insulation xfmr. I measured 60-65V, and 70ľA. This
current is so tiny you won't normally feel it, so no danger to human
beings.
Click to expand...
You might be shocked (pun intended) to learn that capacitors (and other
components) sometimes fail.

However, if some equipment is earthed, and some not, it might
destroy electronics.
Also note that this was in a 220V IT circuit, which means that earth is
nominally floating.
Click to expand...

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.
 
Jim Adney <jadney@vwtype3.org> writes:
On Fri, 10 Jun 2005 21:21:55 -0400 Gary Schafer
gaschafer@comcast.net> wrote:

The doom and gloomers sure do come out of the woodwork.

Yep, I completely agree. It's rather clear that no one before Gary had
much of a clue as to what was really going on here.

What you are seeing is the completely normal result of having a home
system with no ground, a power strip with surge protection, and a
voltmeter with a high imput impedance.

You can leave things just the way they are,
Click to expand...
.....if of course one enjoys the safety and thrill of getting shocked
by your computer case. :) The situation may be relatively common, but
it's far from normal or safe.

The only responsible solution to the OP's quandry is an electrician,
plain and simple.

Then again, what would I know about electricity?

Best Regards,
--
/"\ ASCII Ribbon Campaign | Todd H
\ / | http://www.toddh.net/
X Promoting good netiquette | http://triplethreatband.com/
/ \ http://www.toddh.net/netiquette/ | "4 lines suffice."
 
invadar@mail.com wrote:

I have a broken power output plug on my laptop psu.

It is like a svideo mini din plug but has 4 pins in a roughly
square formation except that the bottom pair of pins are slightly
closer together than the top pair. it has no plastic locator inside the
barrel of the plug but has two indented locators on the outer steel
barrel. The plug is round and has the same outward appearance as the
svideo plugs.


I have tried maplins and RS components but can not find them listed.

As I begrudge paying Ł60 for a new psu for the sake of a plug I would
be most grateful to anyone who could help me source one or who could
give me the proper name for the plug so that I can try further myself.


Thanks in advance Invadar.

I think you have ther correct term: mini-DIN, 4 pin/connector
Click to expand...
(depending on which sex you need to fit or replace).
Here in the colonnies, there are a number of sources; to see what is
available, look in Digikey, Mouser or Jameco.
Digikey: http://dkc3.digikey.com/PDF/T052/0257.pdf
Mouser: http://www.mouser.com/catalog/622/877.pdf
Jameco:
http://www.jameco.com/webapp/wcs/stores/servlet/CatalogSearchResultView?langId=-1&storeId=10001&catalogId=10001&searchType=k&searchValue=mini%20din&categoryId=302010

Basically, use the search facility and tyoe in "mini din" no quotes...
 
On Sat, 11 Jun 2005 12:31:18 -0700 Al Brenan <nannerbac@yahoo.com>
wrote:

On Fri, 10 Jun 2005 23:51:39 -0500, Jim Adney <jadney@vwtype3.org
wrote:

It's rather clear that no one before Gary had
much of a clue as to what was really going on here...

You can leave things just the way they are....

Speaking of clues: if the OP leaves things "just the way they are," he
will have an ever-present and very real 60V potential between his
computer case and the cable shield. That's 60Vrms at 60Hz between
bare, exposed metal conductors possibly just inches apart. Dunno
about you, but I wouldn't want that.
Click to expand...
Sure, it's 60V as seen on a 10 MOhm meter, but the source impedance is
on the order of a MegOhm. That's never going to provide enough current
to be dangerous. Of course that assumes that all his components remain
in good condition. If something actually fails, then you're right and
he is without a safety ground.

He could experiment with this by touching both "grounds" at the same
time and measuring the voltage on his PC chassis at the same time.
He'll discover that he has grounded the PC and that there is no longer
a voltage there.

He's already explained that he gets a shock whenever he touches both
parts. I believe him. The fact that he's done this several times with
no extreme effects implies that it's a perceptable amount of current,
but not a dangerous one. This is what one would expect from a power
strip with surge protection that lacked a ground.

He could probably improve his situation by just grounding his PC to
the cable shield. This carries the possiblity of passing a shock on to
someone working on the cable system, however, so that's why I really
don't recommend it.

And I agree, we would ALL be better off with all grounded outlets, but
there are many old houses around which just don't have them.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------
 
Tristan Beeline wrote:
I need a lot of energy for my laboratory, so it uses a Plutonium - reactor.

Where can I buy the Plutonium for my reactor ?
There is *lots* of that on Pluto...
Click to expand...
 
If that happens, then why does not my GFCI breaker trip?

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "Vidar Lřkken" <njus@vidarlo.net> ?????? ??? ??????
news:UOAqe.1845$qE.484380@juliett.dax.net...
Dimitrios Tzortzakakis wrote:

Is this legal in USA?Here, there are people who put shucko-plugs in old
fashioned three-prong receptacles, with the result, abcence of ground
(the
appliance works, but is not grounded).Modern computers that work in the
GHz
range need very good grounding, because their case becomes hot otherwise
from induced high-frequency currents.


Bullshit. The potential at the case is power leaked in the psu, not
_any_ other parts in the computer. The psu has a filter on the input,
which leaks tiny currents to ground/chassis. This has nothing to do with
the cpu or any other thing. It has nothing to do with induction afaik.


--
MVH,
Vidar

www.bitsex.net
Click to expand...
 
Then why is a computer in a fully enclosure metal case?Provided, that a
computer works with voltages not higher than 12 volt, and the PSU is already
shielded, why not put it in a plastic case?

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "Vidar Lřkken" <njus@vidarlo.net> ?????? ??? ??????
news:xPIqe.1859$qE.489769@juliett.dax.net...
Vidar Lřkken wrote:

Bullshit. The potential at the case is power leaked in the psu, not
_any_ other parts in the computer. The psu has a filter on the input,
which leaks tiny currents to ground/chassis. This has nothing to do with
the cpu or any other thing. It has nothing to do with induction afaik.




Just for fun I measured those values on a atx psu connected to a 100W
load, trough a insulation xfmr. I measured 60-65V, and 70ľA. This
current is so tiny you won't normally feel it, so no danger to human
beings. However, if some equipment is earthed, and some not, it might
destroy electronics.
Also note that this was in a 220V IT circuit, which means that earth is
nominally floating.

--
MVH,
Vidar

www.bitsex.net
Click to expand...
 
Vidar Lřkken wrote:
Vidar Lřkken wrote:

Bullshit. The potential at the case is power leaked in
the psu, not
_any_ other parts in the computer. The psu has a filter
on the input,
which leaks tiny currents to ground/chassis. This has
nothing to do
with the cpu or any other thing. It has nothing to do
with induction
afaik.




Just for fun I measured those values on a atx psu
connected to a 100W
load, trough a insulation xfmr. I measured 60-65V, and
70ľA. This
current is so tiny you won't normally feel it, so no
danger to human
beings. However, if some equipment is earthed, and some
not, it might
destroy electronics.
Click to expand...
According to several references, GFCI designed for personnel
protection will trip when leakage current exceeds 5
milliamps.
 
Dimitrios Tzortzakakis wrote:

Then why is a computer in a fully enclosure metal case?
Click to expand...
Because its pretty hard to make a computer double insulated.

Provided, that
a computer works with voltages not higher than 12 volt,
and the PSU
is already shielded, why not put it in a plastic case?
Click to expand...
See laptops - computers that have voltages < 20 volts
entering their cases and have plastic cases.
 
Dimitrios Tzortzakakis wrote:
Then why is a computer in a fully enclosure metal case?Provided, that a
computer works with voltages not higher than 12 volt, and the PSU is already
shielded, why not put it in a plastic case?
Click to expand...
Because of RF emissions.
It can/will make inteference with other electronic equipment, but it is
not the RF that induces the voltage.
Besides, notebooks is plastic cabinets... And so is the plexiglass
cabinets that is commonplace those days. But you require a common
ground, and so metal is practical, in favour of running a ground cable
to every device.
Also metal is more durable than plastics.
But yes, a computer emits _huge_ mengths of RF, enough to disturb a
radio, but not enough to induce 60V in the chassis. Maybe a few ľV.


--
MVH,
Vidar

www.bitsex.net
 
Arny Krueger wrote:
Dimitrios Tzortzakakis wrote:


Then why is a computer in a fully enclosure metal case?


Because its pretty hard to make a computer double insulated.
Click to expand...
No, not really. The 12V is 12V from ground. Not some 1xx volts from
ground, so it'd not have to be double insulated. The PSU would have to
be, and that would be pretty easy.

Provided, that
a computer works with voltages not higher than 12 volt,

and the PSU

is already shielded, why not put it in a plastic case?


See laptops - computers that have voltages < 20 volts
entering their cases and have plastic cases.
Click to expand...
And doubly so because the PSU leakage is capacitors connected to
gnd/midpoint _on purpose_.

Yes bad habit, replying to post and posts child.

--
MVH,
Vidar

www.bitsex.net
 
On Mon, 13 Jun 2005 14:57:40 +0300, "Dimitrios Tzortzakakis"
<dimtzort@otenet.gr> wrote:

Then why is a computer in a fully enclosure metal case?Provided, that a
computer works with voltages not higher than 12 volt, and the PSU is already
shielded, why not put it in a plastic case?
To provied FCC (and other regulatory) EMI shielding. Many of those
Click to expand...
plastilc looking cases are either coated or contain carbon or other
conductive material. See FCC rules, Part 15

, _
, | \ MKA: Steve Urbach
, | )erek No JUNK in my email please
, ____|_/ragonsclaw dragonsclawJUNK@JUNKmindspring.com
, / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org
 
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