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geoley
Guest
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 Posted:
Thu Nov 03, 2005 4:42 am Post subject:
Grounding |
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I read the story about the church pastor electrocuted when he grabbed a mic
while standing in water. I can see where this can happen. A guitarist friend
of mine had an old guitar amp, I forget what make, and during a gig when his
lips made contact with the mic he was singing into he got a helluva shock
that darn near knocked him down. Later investigation of the amp revealed
that the hot side of the line had gone to chassis ground via a defective
bypass cap. The mic he was singing into was connected to the venues PA
system which was at ground potential. Just shows what can happen
George
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Chel van Gennip
Guest
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| Posted:
Thu Nov 03, 2005 4:55 am Post subject:
Re: Grounding |
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On Wed, 02 Nov 2005 23:42:54 +0100, geoley wrote:
| Quote: | I read the story about the church pastor electrocuted when he grabbed a
mic while standing in water. I can see where this can happen. A
guitarist friend of mine had an old guitar amp, I forget what make, and
during a gig when his lips made contact with the mic he was singing into
he got a helluva shock that darn near knocked him down. Later
investigation of the amp revealed that the hot side of the line had gone
to chassis ground via a defective bypass cap. The mic he was singing
into was connected to the venues PA system which was at ground
potential. Just shows what can happen
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Should propper grounding and a safety switch (switching off mains when a
leakage current of 30mA or so to earth is detected) be standard? In The
Netherlands every instalation build or modified since 1975 should have
this safety switch.
--
Chel van Gennip
Visit Serg van Gennip's site http://www.serg.vangennip.com |
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Scott Dorsey
Guest
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| Posted:
Thu Nov 03, 2005 5:06 am Post subject:
Re: Grounding |
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Chel van Gennip <chel@vangennip.nl> wrote:
| Quote: | On Wed, 02 Nov 2005 23:42:54 +0100, geoley wrote:
I read the story about the church pastor electrocuted when he grabbed a
mic while standing in water. I can see where this can happen. A
guitarist friend of mine had an old guitar amp, I forget what make, and
during a gig when his lips made contact with the mic he was singing into
he got a helluva shock that darn near knocked him down. Later
investigation of the amp revealed that the hot side of the line had gone
to chassis ground via a defective bypass cap. The mic he was singing
into was connected to the venues PA system which was at ground
potential. Just shows what can happen
Should propper grounding and a safety switch (switching off mains when a
leakage current of 30mA or so to earth is detected) be standard? In The
Netherlands every instalation build or modified since 1975 should have
this safety switch.
|
In the US, this safety switch is called a GFI (Ground Fault Interruptor)
and it's been required for about 20 years in any wet environments. You
will see them in bathrooms, and of course they are required on swimming
pool (and baptismal font) heaters and pumps.
But you won't see them in most stage environments, aside from outdoor
stages. In part this is because they can trip too easily.
Still, the problem mentioned above can be prevented by retrofitting a
three-prong power cord onto the amp, which is something that EVERY
amp should be equipped with today.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis." |
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Les Cargill
Guest
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| Posted:
Thu Nov 03, 2005 5:42 am Post subject:
Re: Grounding |
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geoley wrote:
| Quote: | I read the story about the church pastor electrocuted when he grabbed a mic
while standing in water. I can see where this can happen. A guitarist friend
of mine had an old guitar amp, I forget what make, and during a gig when his
lips made contact with the mic he was singing into he got a helluva shock
that darn near knocked him down. Later investigation of the amp revealed
that the hot side of the line had gone to chassis ground via a defective
bypass cap. The mic he was singing into was connected to the venues PA
system which was at ground potential. Just shows what can happen
George
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Yeah, the old "cap of death".
--
Les Cargill |
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mainmachine
Guest
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| Posted:
Thu Nov 03, 2005 5:42 am Post subject:
Re: Grounding |
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this cap is referred to as the "death cap" for a reason!
-daver |
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