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#1
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
Hi All,
I have a question relating to plugging my PC into my new 7.1 Amplifier. To cut to the point, the Coaxial lead coming out of the back of my PC's sound card digital out(builtin Nvidia Nforce1) gives me a small shock while holding the end of it (the metal bit) and touching any electronic equipments metal surface at the same time. When plugging-in , unplugging into the amp I got a small shock. Naturally I suppose all electrical leads have power but this seems unusal. My question is: Is this normal? I've never known Analog style RCA Red & White leads to supply enough energy to shock someone (even minimally). I would want to hold it for more than a second... This is a new amplifier and although I'd love to continue to use my computers' 5.1 Coax Out, I'm not too keen if it isn't safe. When i received this shock, the Set-Top-Box I have connected to the Amp turned off! , or at least the TV output went black.. i was worried. I simply reset the STB. It doesn't seem to be related to the Amp or the Coax Rca style lead i'm using... Is my computer healthy? Thanks to anyone who has any idea what is going on here! |
#2
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
Thanks François,
how would I best check whether or not my computer is 'grounded'? I'm thinking it could be a problem with the cable plugged into the power supply, the power supply itself, or something else connected to it that isn't grounded properly. I don't actually have anything else connected that uses mains power though... Would you agree that it wouldn't be wise to plug this cable in (its unusal to get this kind of current isn't it?) François Yves Le Gal wrote: On 19 Jun 2006 05:23:11 -0700, "nilo" wrote: . Is my computer healthy? This is typically a ground related problem, with some runaway currents generated by your PC. Check that it's properly grounded, that the digital out is OK etc. |
#3
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"nilo" wrote ...
I have a question relating to plugging my PC into my new 7.1 Amplifier. To cut to the point, the Coaxial lead coming out of the back of my PC's sound card digital out(builtin Nvidia Nforce1) gives me a small shock while holding the end of it (the metal bit) and touching any electronic equipments metal surface at the same time. When plugging-in , unplugging into the amp I got a small shock. Naturally I suppose all electrical leads have power but this seems unusal. My question is: Is this normal? I've never known Analog style RCA Red & White leads to supply enough energy to shock someone (even minimally). I would want to hold it for more than a second... NO! It is NOT normal. You have a potentially lethal problem somewhere among your equipment. The "ground" side of all your equipment (and the attached cables/connectors) should all be at "ground/earth potential" (i.e. zero volts). Suggest immediately abandoning use of this setup until you diagnose and remedy the problem. Your life is literally on the line here. If you don't have a small multi-meter, suggest getting one NOW. I have seen them even at "home store" places for $5-10. Start on the 200-300V AC range and work down from there to measure the voltage between your two pieces of equipment. If you can feel it, it is likely at least a couple dozen volts. "Normal" is zero. This is a new amplifier and although I'd love to continue to use my computers' 5.1 Coax Out, I'm not too keen if it isn't safe. When i received this shock, the Set-Top-Box I have connected to the Amp turned off! , or at least the TV output went black.. i was worried. I simply reset the STB. It doesn't seem to be related to the Amp or the Coax Rca style lead i'm using... Is my computer healthy? Thanks to anyone who has any idea what is going on here! Does "set-top box" imply some kind of connection to television cable system? That is the first place to suspect a problem. First, disconnect the RF cable from the cable system and measure the voltage between the outside shell of the cable connector and the back of the set-top box. This is a very common place for bad ground problems because the cable system is referenced to a different ground than your electrical power mains. There are several sources of isolation transformers that you can put in-line with the cable to break this grounding problem. I can't emphasize enough that this is a potentially lethal problem. DO NOT continue grabbing the ends of your cables to feel the shock. |
#4
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"François Yves Le Gal" wrote ...
"nilo" wrote: how would I best check whether or not my computer is 'grounded'? Check your local mains wiring as well as your STB connexions. I'm thinking it could be a problem with the cable plugged into the power supply, the power supply itself, or something else connected to it that isn't grounded properly. I don't actually have anything else connected that uses mains power though... The STB can see DC transmitted thru the cable network. But that is on the inner conductor which is isolated from the rest of your system. OTOH, the STB can also see *considerable* AC difference between the cable system's notion of "ground" and the ground in your house. Voltages in the mid-50s have been reported in these newsgroups. At least that is the way the systems are engineered here in the USA, for better or for worse. And that is why people sell (and buy) cable isolation transformers. |
#5
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
I must add, I am using this death trap computer right now, and have
done for a few years now... but I've only just noticed this current when plugging into its digital audio out...odd I think I'm gonna have to take a short course in basic electricity and learn how to use a multimeter, because it doesn't sound like amatuer stuff nilo wrote: Okay Okay Thanks Richard... but I don't think i was quite as clear as I should have been.,, Disregarding my Amp, TV, SetTopBox, .. My PC is putting out current that can give a slight shock on its Coax Digital Audio Out line ... I just want to know is it normal to feel this kind of current from touching anything coming out of anything you can easily touch out of the back of a PC? I tried an altervative RCA cable.. this ( i hope is what an ordinary to wire analog style audio lead is called).. A Set-Top-Box is what we call Free-to-air Digital Television recievers in Australia... we don't have Cable TV only the Satellite Pay TV which thankgod I haven't got because I watch enough free TV :P nilo nilo wrote: Hi All, I have a question relating to plugging my PC into my new 7.1 Amplifier. To cut to the point, the Coaxial lead coming out of the back of my PC's sound card digital out(builtin Nvidia Nforce1) gives me a small shock while holding the end of it (the metal bit) and touching any electronic equipments metal surface at the same time. When plugging-in , unplugging into the amp I got a small shock. Naturally I suppose all electrical leads have power but this seems unusal. My question is: Is this normal? I've never known Analog style RCA Red & White leads to supply enough energy to shock someone (even minimally). I would want to hold it for more than a second... This is a new amplifier and although I'd love to continue to use my computers' 5.1 Coax Out, I'm not too keen if it isn't safe. When i received this shock, the Set-Top-Box I have connected to the Amp turned off! , or at least the TV output went black.. i was worried. I simply reset the STB. It doesn't seem to be related to the Amp or the Coax Rca style lead i'm using... Is my computer healthy? Thanks to anyone who has any idea what is going on here! |
#6
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"nilo" wrote ...
Okay Okay Thanks Richard... but I don't think i was quite as clear as I should have been.,, Disregarding my Amp, TV, SetTopBox, .. My PC is putting out current that can give a slight shock on its Coax Digital Audio Out line ... I can't emphasize enough that what feels like "a slight shock" with dry skin CAN KILL YOU under the "right" conditions. Fix this now before it is too late. |
#7
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
On Mon, 19 Jun 2006 07:57:22 -0700, Richard Crowley wrote:
"nilo" wrote ... Okay Okay Thanks Richard... but I don't think i was quite as clear as I should have been.,, Disregarding my Amp, TV, SetTopBox, .. My PC is putting out current that can give a slight shock on its Coax Digital Audio Out line ... I can't emphasize enough that what feels like "a slight shock" with dry skin CAN KILL YOU under the "right" conditions. Fix this now before it is too late. Yes. I recomend that you don't strip naked and make the connections in the tub. |
#8
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
In article , "Richard Crowley" wrote:
"François Yves Le Gal" wrote ... "nilo" wrote: how would I best check whether or not my computer is 'grounded'? Check your local mains wiring as well as your STB connexions. I'm thinking it could be a problem with the cable plugged into the power supply, the power supply itself, or something else connected to it that isn't grounded properly. I don't actually have anything else connected that uses mains power though... The STB can see DC transmitted thru the cable network. But that is on the inner conductor which is isolated from the rest of your system. OTOH, the STB can also see *considerable* AC difference between the cable system's notion of "ground" and the ground in your house. Voltages in the mid-50s have been reported in these newsgroups. At least that is the way the systems are engineered here in the USA, for better or for worse. And that is why people sell (and buy) cable isolation transformers. I also understand that the cable should be grounded separately as it comes into the building. I may be wrong, but it seems like the thing to do anyway. greg |
#9
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
nilo wrote: Hi All, I have a question relating to plugging my PC into my new 7.1 Amplifier. To cut to the point, the Coaxial lead coming out of the back of my PC's sound card digital out(builtin Nvidia Nforce1) gives me a small shock while holding the end of it (the metal bit) and touching any electronic equipments metal surface at the same time. It's an earthing problem. Graham |
#10
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
Richard Crowley wrote:
If you can feel it, it is likely at least a couple dozen volts. "Normal" is zero. Normal isn't zero any more. Normal is for nothing to be earthed. Any component will have a leakage current of less than a milliamp, which is legal, but when you connect up an amp, tv, dvd player etc., then any exposed metal will be floating at 50 or a hundred volts and can deliver several milliamps. My guess is that the PC is grounded properly and the shock is from and touching any electronic equipments metal surface at the same time. -- Eiron No good deed ever goes unpunished. |
#11
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
Eiron wrote: Normal is for nothing to be earthed. Not for PCs. Graham |
#12
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
Pooh Bear wrote:
Eiron wrote: Normal is for nothing to be earthed. Not for PCs. Normal is for nothing to be earthed except PCs. And the solution is to turn everything off at the wall before connecting the PC's digital coax to the amp. -- Eiron No good deed ever goes unpunished. |
#13
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
nilo wrote:
I must add, I am using this death trap computer right now, and have done for a few years now... but I've only just noticed this current when plugging into its digital audio out...odd I think I'm gonna have to take a short course in basic electricity and learn how to use a multimeter, because it doesn't sound like amatuer stuff sf your PC using a 2-wire IEC mains lead rather than the required 3-pins (wires !). 2-pin ones are available for double-insulated appliances, but are death-traps when used with appliances that require an earth. geoff |
#14
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"GregS" wrote ...
I also understand that the cable should be grounded separately as it comes into the building. I may be wrong, but it seems like the thing to do anyway. The TV cable *is* grounded. It is "code" in most places, at least here in North America. The problem is not that it isn't grounded, the problem is that the ground reference of the cable system is sometimes quite far away from the ground reference for *your house* (both geographically "far away" and electrically "far away). |
#15
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"Richard Crowley" wrote in message ... I can't emphasize enough that what feels like "a slight shock" with dry skin CAN KILL YOU under the "right" conditions. Fix this now before it is too late. Maybe you should also emphasise the fact that many devices have enough leakage to give you quite a tingle, but not enough to kill you. The days of every chassis/case being tied to a local ground are long gone. MrT. |
#16
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"Mr.T" wrote: "Richard Crowley" wrote in message ... I can't emphasize enough that what feels like "a slight shock" with dry skin CAN KILL YOU under the "right" conditions. Fix this now before it is too late. Maybe you should also emphasise the fact that many devices have enough leakage to give you quite a tingle, but not enough to kill you. The days of every chassis/case being tied to a local ground are long gone. There are regulations for Class II ( double insulated ) products. The leakage current should not be enought to cause a tingle. I've seen tiny sparks when plugging such things in though ( my printer in fact ) ! Graham |
#17
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"Mr.T" wrote ...
"Richard Crowley" wrote ... I can't emphasize enough that what feels like "a slight shock" with dry skin CAN KILL YOU under the "right" conditions. Fix this now before it is too late. Maybe you should also emphasise the fact that many devices have enough leakage to give you quite a tingle, but not enough to kill you. It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. The days of every chassis/ case being tied to a local ground are long gone. But equipment without protective grounding is required to have significant "double insulation" instead. Thankfully, there are people more knowledgable about these things watching out for your safety. |
#18
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
On Tue, 20 Jun 2006 05:38:39 -0700, "Richard Crowley"
wrote: It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. Amps kill, not volts. Else we'd all be dead many times over from static discharges. |
#19
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
On Tue, 20 Jun 2006 14:03:48 +0100, Laurence Payne
lpayne1NOSPAM@dslDOTpipexDOTcom wrote: On Tue, 20 Jun 2006 05:38:39 -0700, "Richard Crowley" wrote: It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. Amps kill, not volts. Else we'd all be dead many times over from static discharges. The old canard again! The body has a resistance. To get current to flow through that resistance you need volts (Ohms law applies here as it does everywhere). If the source resistance of the electricity is too great to let much current flow, you won't get the volts. Simple really. If you have the volts, you will have the amps. d -- Pearce Consulting http://www.pearce.uk.com |
#20
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
On Tue, 20 Jun 2006 14:03:48 +0100, Laurence Payne lpayne1NOSPAM@dslDOTpipexDOTcom wrote:
On Tue, 20 Jun 2006 05:38:39 -0700, "Richard Crowley" wrote: It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. Amps kill, not volts. Else we'd all be dead many times over from static discharges. Yes, but current equals volts divided by resistance. For a given resistance, amperage is proportional to voltage. Static is not a problem because of it's voltage dies off almost instantly. Ground yourself well and grab a well charged van de graff generator and you'll be singing a different story about harmless static electricity. |
#21
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
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#22
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
On Tue, 20 Jun 2006 13:46:22 GMT, AZ Nomad
wrote: It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. Amps kill, not volts. Else we'd all be dead many times over from static discharges. Yes, but current equals volts divided by resistance. For a given resistance, amperage is proportional to voltage. Static is not a problem because of it's voltage dies off almost instantly. Ground yourself well and grab a well charged van de graff generator and you'll be singing a different story about harmless static electricity. Sure. And lightning can kill. But a lot of perfectly real static voltages we run across in everyday life can't. A rather clumsy straw man, that :-) |
#23
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
On Tue, 20 Jun 2006 17:47:32 +0100, Laurence Payne
lpayne1NOSPAM@dslDOTpipexDOTcom wrote: On Tue, 20 Jun 2006 13:10:37 GMT, (Don Pearce) wrote: Amps kill, not volts. Else we'd all be dead many times over from static discharges. The old canard again! The body has a resistance. To get current to flow through that resistance you need volts (Ohms law applies here as it does everywhere). If the source resistance of the electricity is too great to let much current flow, you won't get the volts. Simple really. If you have the volts, you will have the amps. Go on then. Measure a few Kv of static and see how many amps you can draw. The voltage is real and measurable. But there's no amps behind it. Likewise, use the (very real) voltage between the cable TV "ground" and your "ground" to do some useful work. That 60v should at least run a table lamp? I've done plenty of static measurements when I had to design a test system for radiopagers. With typical static sources I was measuring between 10 and 100 amps. The point is that the pulse is very brief as there is very little charge behind it all. It is the coulombs, not the amps that are missing. As for the PD on a TV, yes it is typically at about half mains voltage, but that is coupled through a very small capacitance - plenty enough to run a DMM up to true volts, but not capable of holding up to deliver current. Even grabbing it by hand, you will typically get a brief zap, followed by very little. d -- Pearce Consulting http://www.pearce.uk.com |
#24
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"Laurence Payne" wrote...
"Richard Crowley"wrote: It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. Amps kill, not volts. Else we'd all be dead many times over from static discharges. Oh, here we go again. Volts kill. It only takes a few mA to stop your heart. Actually, it is volts * amps = charge. What do you think they are talking about when the TV doctor tells the nurse to charge the paddles up to "300" to revive the patient's stopped heart? Why do you think they yell "clear!" before applying the charge? If amps killed, we'd all be dead every time we exchanged our car battery (good for 300-400 Amperes!) |
#25
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"Laurence Payne" wrote ...
Sure. And lightning can kill. But a lot of perfectly real static voltages we run across in everyday life can't. A rather clumsy straw man, that :-) And there are just as many (or maybe more) cases where someone was struck by lightning and they lived to tell about it. Depends on how much charge when through them, and whether the current went through any critical circuits (cardiac, etc.) |
#26
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
On Tue, 20 Jun 2006 17:49:23 +0100, Laurence Payne lpayne1NOSPAM@dslDOTpipexDOTcom wrote:
On Tue, 20 Jun 2006 13:46:22 GMT, AZ Nomad wrote: It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. Amps kill, not volts. Else we'd all be dead many times over from static discharges. Yes, but current equals volts divided by resistance. For a given resistance, amperage is proportional to voltage. Static is not a problem because of it's voltage dies off almost instantly. Ground yourself well and grab a well charged van de graff generator and you'll be singing a different story about harmless static electricity. Sure. And lightning can kill. But a lot of perfectly real static voltages we run across in everyday life can't. Yes, because a microsecond later, they're under ten volts. Using static electricity as an example of how high voltage can be OK ignores the fact that the high voltage vanishs almost immediately. |
#27
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
Richard Crowley wrote: "Laurence Payne" wrote... "Richard Crowley"wrote: It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. Amps kill, not volts. Else we'd all be dead many times over from static discharges. Oh, here we go again. Yes, we all are flying lose and free with terminology and concepts. Volts kill. It only takes a few mA to stop your heart. That's true, but... Actually, it is volts * amps = charge. No, volts*amps is NOT charge. volts*amps is power, measured in watts. Charge is measured in coulombs. What do you think they are talking about when the TV doctor tells the nurse to charge the paddles up to "300" to revive the patient's stopped heart? They are saying 300 WATT-SECONDS, or 300 joules. They are talking units of ENERGY, not POWER or CHARGE. Why do you think they yell "clear!" before applying the charge? So everybody can see the patient jump and make googly eyes? If amps killed, we'd all be dead every time we exchanged our car battery (good for 300-400 Amperes!) Look, so far, NOBODY has got it right or even remotely complete. The fact is that electrical conduction through living tissue is highly non-linear. Under small potential differences, the electrical conductivity of tissue through the skin is pretty damned low, and thus the current is similarily low It's not until enough potential exists that sufficient polarization occurs that you actually get conduction. Under such circumtances, the conductivity drops and, if there is sufficient energy left, then the current starts increasing. Now, IF the current is sufficient AND the path is right, the current can repolarize the conduction channels in the cells in muscles and then there's hell to pay. If the muscles are near the surface of the skin, then the effect could be anything from a light buzzing sensation to a sudden contraction. If one of those muscles happens to be in the ehart, well, a different problem occurs. All sorts of conditions can change the outcome. Grab on to a sufficient potential difference when you're hot, dirty, dripping in sweat and a lot of current could pass, but the effect could be no more than a sudden urge to drop whatever it is you're holding NOW! The vast majority of the current flows in the rather conductive surface moisture on the skin. I myself have been witness to such a case where the subject accidently got across of 280 V leg of a three-phase tarnsformer and drew enough current to blow a breaker, yet walked away with nothing more than a sore back because the person jumped and fell. And I have also been witness to someone who almost killed themselves with about a 20 volt potential between right knee and left shoulder when the air was cool, dry and most conduction occured through the skin, but the evidence indicated that it took several seconds for the conduction to get going. But to those who say that it's voltage and not amps, you're wrong. To those that say it's amps that kill and not volts, you're wrong also. And to thopse that say the original poster is dealing with a potentially hazardous situation, well, maybe yes, maybe no. But precisely what service is being done to this person in debating on woefully incomplete data and potentially dragging him down a rosey garden path with tigers hiding in the bushes. To that poster: find comeone competent to deal with the issue and FIX IT! |
#28
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
On Tue, 20 Jun 2006 10:12:54 -0700, Richard Crowley wrote:
If amps killed, we'd all be dead every time we exchanged our car battery (good for 300-400 Amperes!) Another person clueless of ohms law. If you touch that battery, you're only pulling a few microamps. |
#29
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
On 6/20/2006 11:49 AM, Laurence Payne wrote:
On Tue, 20 Jun 2006 13:46:22 GMT, AZ Nomad wrote: It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. Amps kill, not volts. Else we'd all be dead many times over from static discharges. Yes, but current equals volts divided by resistance. For a given resistance, amperage is proportional to voltage. Static is not a problem because of it's voltage dies off almost instantly. Ground yourself well and grab a well charged van de graff generator and you'll be singing a different story about harmless static electricity. Sure. And lightning can kill. But a lot of perfectly real static voltages we run across in everyday life can't. A rather clumsy straw man, that :-) Stand on your right foot and use your right hand. Then the current will miss your heart. |
#30
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
Don Pearce wrote:
As for the PD on a TV, yes it is typically at about half mains voltage, but that is coupled through a very small capacitance - plenty enough to run a DMM up to true volts, but not capable of holding up to deliver current. Even grabbing it by hand, you will typically get a brief zap, followed by very little. -- Eiron No good deed ever goes unpunished. |
#31
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
"SD" wrote ...
Stand on your right foot and use your right hand. Then the current will miss your heart. Is that why left-handed people die younger? |
#32
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
dpierce wrote ...
Richard Crowley wrote: Actually, it is volts * amps = charge. No, volts*amps is NOT charge. volts*amps is power, measured in watts. Charge is measured in coulombs. Bzzzt! You are right, of course. I shouldn't try thinking before I wake up. Why do you think they yell "clear!" before applying the charge? So everybody can see the patient jump and make googly eyes? LOL! The "googly eyes" part is more Hollywood than "Real Life". But to those who say that it's voltage and not amps, you're wrong. To those that say it's amps that kill and not volts, you're wrong also. If I can try to defend myself, my theory was that it takes enough voltage to make it through the relatively high- impedance epidermis. OTOH, you could say the same thing about current from the other side of the Ohm's Law see-saw. And to thopse that say the original poster is dealing with a potentially hazardous situation, well, maybe yes, maybe no. But precisely what service is being done to this person in debating on woefully incomplete data and potentially dragging him down a rosey garden path with tigers hiding in the bushes. To that poster: find comeone competent to deal with the issue and FIX IT! Thanks. That all I was trying to say. |
#33
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
Richard Crowley wrote: "Mr.T" wrote ... "Richard Crowley" wrote ... I can't emphasize enough that what feels like "a slight shock" with dry skin CAN KILL YOU under the "right" conditions. Fix this now before it is too late. Maybe you should also emphasise the fact that many devices have enough leakage to give you quite a tingle, but not enough to kill you. It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. The days of every chassis/ case being tied to a local ground are long gone. But equipment without protective grounding is required to have significant "double insulation" instead. Thankfully, there are people more knowledgable about these things watching out for your safety. Class II ( double insulated ) equipment is still allowed to have a significant ( 1mA ) leakage current though. Graham |
#34
Posted to rec.audio.tech
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Is Coax-Digital Usually High Voltage !@!#??
Laurence Payne wrote: On Tue, 20 Jun 2006 13:10:37 GMT, (Don Pearce) wrote: Amps kill, not volts. Else we'd all be dead many times over from static discharges. The old canard again! The body has a resistance. To get current to flow through that resistance you need volts (Ohms law applies here as it does everywhere). If the source resistance of the electricity is too great to let much current flow, you won't get the volts. Simple really. If you have the volts, you will have the amps. Go on then. Measure a few Kv of static and see how many amps you can draw. The voltage is real and measurable. But there's no amps behind it. Likewise, use the (very real) voltage between the cable TV "ground" and your "ground" to do some useful work. That 60v should at least run a table lamp? Oh, there's plenty of amps there, just not many Joules ! Graham |
#35
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Is Coax-Digital Usually High Voltage !@!#??
Richard Crowley wrote: If I can try to defend myself, my theory was that it takes enough voltage to make it through the relatively high- impedance epidermis. You reckon the epidermis works like a zener diode ? Maybe you're right ? Graham |
#36
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Is Coax-Digital Usually High Voltage !@!#??
"Richard Crowley" wrote in message ... It takes quite a bit of voltage to make it through your high-impedance epidermis. Several times more voltage that it would take to kill you under conditions where your high skin resistance were lowered via any number of conditions. Fortunately there is a minimum current required to kill you, and a high impedance source can not provide it. The days of every chassis/ case being tied to a local ground are long gone. But equipment without protective grounding is required to have significant "double insulation" instead. Exactly, and if you understood the problem you'd know that's why you can still get a tingle from metal connectors. (switch mode power supplies are often the cause) Thankfully, there are people more knowledgable about these things watching out for your safety. Which is why I have had tingles from many double insulated devices I guess. They are obviously failing to do their job then, in your opinion. Maybe you think we need regulations to stop us getting a shock from nylon carpet, or car seat covers as well? Have many people died from those I wonder. MrT. |
#37
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Is Coax-Digital Usually High Voltage !@!#??
"Don Pearce" wrote in message ... Amps kill, not volts. Else we'd all be dead many times over from static discharges. The old canard again! You have never had an electrostic shock then? The body has a resistance. To get current to flow through that resistance you need volts (Ohms law applies here as it does everywhere). If the source resistance of the electricity is too great to let much current flow, you won't get the volts. Simple really. Maybe, if you were talking about a permanently connected circuit. It's what happens at the instant the person touches the voltage that causes the shock. If the shock continues indefinitelty, there is indeed a fault condition! If you have the volts, you will have the amps. If you have enough *source impedance* you will NOT have many amps, regardless of open circuit voltage. Simple really. MrT. |
#38
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Is Coax-Digital Usually High Voltage !@!#??
"Don Pearce" wrote in message ... As for the PD on a TV, yes it is typically at about half mains voltage, but that is coupled through a very small capacitance - plenty enough to run a DMM up to true volts, but not capable of holding up to deliver current. Even grabbing it by hand, you will typically get a brief zap, followed by very little. I'm glad you now agree you *can* get a zap from a non faulty device, and not die. Seems like your rant was over nothing. MrT. |
#39
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Is Coax-Digital Usually High Voltage !@!#??
On Wed, 21 Jun 2006 13:59:37 +1000, "Mr.T" MrT@home wrote:
"Don Pearce" wrote in message ... As for the PD on a TV, yes it is typically at about half mains voltage, but that is coupled through a very small capacitance - plenty enough to run a DMM up to true volts, but not capable of holding up to deliver current. Even grabbing it by hand, you will typically get a brief zap, followed by very little. I'm glad you now agree you *can* get a zap from a non faulty device, and not die. Seems like your rant was over nothing. MrT. Rant? I don't remember one of those. d -- Pearce Consulting http://www.pearce.uk.com |
#40
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Is Coax-Digital Usually High Voltage !@!#??
On Wed, 21 Jun 2006 13:56:33 +1000, "Mr.T" MrT@home wrote:
"Don Pearce" wrote in message ... Amps kill, not volts. Else we'd all be dead many times over from static discharges. The old canard again! You have never had an electrostic shock then? The body has a resistance. To get current to flow through that resistance you need volts (Ohms law applies here as it does everywhere). If the source resistance of the electricity is too great to let much current flow, you won't get the volts. Simple really. Maybe, if you were talking about a permanently connected circuit. It's what happens at the instant the person touches the voltage that causes the shock. If the shock continues indefinitelty, there is indeed a fault condition! If you have the volts, you will have the amps. If you have enough *source impedance* you will NOT have many amps, regardless of open circuit voltage. Simple really. MrT. If you have the source resistance, you don't get the volts. Simple really. d -- Pearce Consulting http://www.pearce.uk.com |
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