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Old 1st October 2003, 12:42 PM   #11
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Default Corona Cows

"My father in law raises cows. Should I visit his farm and install ground straps around his cows in the middle, to be on the save side? "

Obviously the answer is to have the live stock where corona hats to disipate ground traveling ion fields before they discharge.

Methinks this grooming product must have been attempting the same results:
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Old 1st October 2003, 02:34 PM   #12
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Default Re: Corona Cows

Quote:
Originally posted by Da5id4Vz
"My father in law raises cows. Should I visit his farm and install ground straps around his cows in the middle, to be on the save side? "

Obviously the answer is to have the live stock where corona hats to disipate ground traveling ion fields before they discharge.

Methinks this grooming product must have been attempting the same results:
Now I have a picture in my mind of Elsie with a curb feeler wrapped around her mid-section and a Jocko-Devo hat on its head.
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Old 1st October 2003, 04:20 PM   #13
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Default Isolation

Mattyo5

A lot of us go to great trouble rid our systems and test equipment from 60Hz interference or hum. Sometime this is the only way except for purchasing transformers in bulk. I don't intend to do that. Also, it's normal for a fuse to blow before you get a hot chassis, you do have fused equipment right.

Sound like a grounding rod for cows and horses won't work either.

Later
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Old 1st October 2003, 05:37 PM   #14
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Jewilson, please read this thread

Please help.... Grounding issue, and 60 Hz hum

I'm only mentioning this because this is what I have been told. You can argue it out w/ the moderators.

Yes I use fuses. And yes, I go to great lengths to rid my system of hum as well...but removing earth bonds to chassis (not to power supply necessarily) ground is a bad idea.

-Matthew K. Olson
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Old 2nd October 2003, 03:13 AM   #15
haldor is offline haldor  United States
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Default Re: CowPow!

Quote:
Originally posted by Fred Dieckmann
"FYI, do you know why cow and horses are more vunerable to lighting than other animals? Their front feet and back feet are too far apart. If lighting strikes sufficiently close, the induced potential at one end of a cow is enough different from that at the other end to cause current flows lengthwise through the cow's body which stops it's heart."

My father in law raises cows. Should I visit his farm and install ground straps around his cows in the middle, to be on the save side?
Hi Fred,

No ground straps needed, just hobble the little blighters so their feet can't get too far apart.

Phil
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Old 2nd October 2003, 03:38 AM   #16
haldor is offline haldor  United States
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Default Re: Isolation

Quote:
Originally posted by jewilson
Mattyo5

A lot of us go to great trouble rid our systems and test equipment from 60Hz interference or hum. Sometime this is the only way except for purchasing transformers in bulk. I don't intend to do that. Also, it's normal for a fuse to blow before you get a hot chassis, you do have fused equipment right.
Hi jewilson,

The problem is what happens when your transformer or mains wiring develops a short to the chassis of your enclosure. This is not inconceivable, transformer fail (especially when run hot for prolonged periods of time). Wiring can fail, especially if you neglected to use heat shrink tubing on mains wiring connections or did not carefully route and secure the mains wiring to prevent pinch points. Also I don't understand how a fuse could provide any protection from a short in the wiring before the fuse. Fuses are to protect the expensive transformer from downstream failures, not to prevent an electrocution.

If the enclosure is grounded, then a short will result in large ground fault currents and the circuit breaker in your house will trip, protecting you and your loved ones from electrocution. This is how things are supposed to work.

If the enclosure is not grounded, then there will not be sufficient additional current flow in the hot leg to blow a fuse or trip the AC breaker. A GFI breaker may detect the unbalanced currents in the Hot and Return leads and trip, but a traditional breaker will not detect this condition. This means that the full mains voltage will still be present on the enclosure waiting for someone to touch it. Don't forget that the amount of current required to kill is well under 100 mA.

Phil
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Old 2nd October 2003, 04:28 PM   #17
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Default Phil, Phil. Phil

Look I am not demanding that you are anyone else remove there ac ground returns from there cables. Having said that, I have been doing it for years no ill effect yet. In fact audio equipment has not always come with these AC grounds.

The fact is like I stated if some piece of equipment short, even in the transformer it will pop the inline AC fuse. If the diode bridge fails, it will pop the fuse.
Next you might try working on equipment that has a floating ground while you scope is connected to ground. It will not work.

So if you wire you house with all home run ac out lets you will have ground loops. When you connect equipment to multiple out lets. This is called circulating ground current.

Next yea GFI are great, but put a high current amp on one and see what happens. Also, I never use my amp where it wet.


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Old 2nd October 2003, 05:12 PM   #18
00940 is offline 00940  Belgium
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hum, I just realized that I had a tube amp running without earth. And no way to get one since my old outlet has no ground.

I just went back to my old manuals and .... Could I use an isolation transformer instead of earth ? More specifically, I've still at home one old heavy EI core stepdown transformer. It has jumpers for 1:1 and is rated for 600W (the amp is rated at 2w).
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Old 2nd October 2003, 05:30 PM   #19
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Default AC ground

The AC ground is on the third prong and connects to your chassis ground.
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Old 2nd October 2003, 10:11 PM   #20
haldor is offline haldor  United States
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Default Re: Phil, Phil. Phil

Quote:
Originally posted by jewilson
Phil, Phil. Phil

The fact is like I stated if some piece of equipment short, even in the transformer it will pop the inline AC fuse. If the diode bridge fails, it will pop the fuse.
Jim, lose the superior tone, it doesn't make your arguments more persuasive.

There are lots of failure modes that will blow the fuse: shorted power supply cap, bridge rectifer, output device whatever. But if you short an AC hot lead to an ungrounded enclosure then the fuse will not blow, instead the enclosure will have AC mains voltage on it.

The only way a fuse will blow is if you draw more current through it than it is rated for. Unless the return lead also gets shorted to the enclosure, shorting the hot lead to the enclosure will not cause any significant increase in current flow. Ground the case like you are supposed to and the fuse will blow when the hot lead is shorted no matter what is going on with the return. Also you neglected the issue of what happens if the AC wiring before the fuse shorts.

I know that people use a power ground adapter (otherwise known as a "Widowmaker" in the live sound biz) to lift power ground, and get away with it. That don't make it smart or safe. Stop suggesting that dangerous behavior is "OK".

P.S. If you are using a ground adapter with a scope be very careful were you put your hands. I use a 1:1 isolation power transformer when working on gear that doesn't have transformer isolated power supplies (like TV's).

Phil
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