Cheater plug...Really dangerous??

Discussion in 'Archived Threads 2001-2004' started by Levesque, Jul 29, 2002.

  1. Levesque

    Levesque Supporting Actor

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    After doing everything, the only thing working to completely remove hum from my tweeters is to use a cheater plug. Is it safe?? Really dangerous??

    Thank.
     
  2. Rick Guynn

    Rick Guynn Second Unit

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    The sole purpose of the 3rd lug on 'grounded' plugs is to provide a conductive path for electricity should the positive lead somehow get shorted to the casing. Should such a thing happen, that 3rd lug completes a 'short' circuit which should trip a breaker/blow a fuse. If the third lug was not there, then the casing would remain elctrified until someone touches it, thereby providing another electrcal path (and giving that person a real jolt).

    I have personally never known anyone who has encountered this situation, but I'm sure it has happened somewhere. Given all of that info, though, I'll let you decide how safe it is for yourself.

    RG
     
  3. Chu Gai

    Chu Gai Lead Actor

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    I'd urge against their use. You just need to track down the source of the loop and address it.
     
  4. Russell _T

    Russell _T Supporting Actor

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    It's interesting that Hsu ships a cheater plug in the box with their subwoofers. I would think this could be a nasty liability issue for them. I'm using it though [​IMG] mainly because there is a nasty hum otherwise.
     
  5. Kevin T

    Kevin T Screenwriter

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    in this instance, i imagine one could attempt to draw a parallel between a cheaper plug connected to an amp and a loaded handgun. as long as you and everyone else is aware of it's potential danger and treat it with the respect and caution it deserves...there shouldn't be any problems. but i would personally advise you follow chu's advice. better safe than sorry...you know.

    kevin t
     
  6. Chu Gai

    Chu Gai Lead Actor

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    This seems to be a continuation from somewhere else. Take a look at this link which has some discussions on groundloops.
     
  7. Jeremy Hegna

    Jeremy Hegna Supporting Actor

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    It is NOT that dangerous. If your home is wired to todays specs, your fuse/breaker will cut before you get shocked. If there is an internal short in your amplifier, it will act just as if there were a wire short and trip the breaker.


    The reason no one has heard about it is because the chances are almost slim to none. Solid State electronics are incredibly safe these days. There is no reason to consider using a cheater plug a significant risk. In the older days of electricity, yes...today, no.

    Most of todays amplifiers and heavy duty electrical using components also have their own internal fuse. If there was a problem within the unit electrically, it will toast it's own fuse before you can reach it to turn it off.

    Just my $.02


    Jeremy
     
  8. Claude M

    Claude M Stunt Coordinator

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    Use the cheater plug then take a VOM and see if the chassis is grounded. I bet it is. Not every house is up to new code, many have some old wiring left in them (like mine). I can't see having the chassis twist in the wind. I bet the TA is providing a ground for that chassis. The cheater plug on small electronic equipment is safe. However, do not try this with an AC or fridge! They are wired different, and if the line does not have that ground get it installed! It WILL kill you if grn not present. I speak from personal experience. My basement fridge had no ground. My wife said to me "every time I open that fridge I feel a small shock" (we had just purchased the house). I felt the shock too but thought it was just in my head and dismissed it. But since she mentioned it, I investigated further. Took the VOM to a copper water pipe directly above the fridge and the door to the fridge. The voltage was 120VAC between door and pipe! Nice! The outlet/line was new on a dedicated circuit. The @sswipe that installed the line never connected the ground. Easy fix, connected the grn. on each end (breaker box and outlet) and all was well.
     
  9. Levesque

    Levesque Supporting Actor

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    LOL. It's what I tought. It's impossible to get a clean answer on this one. I will ask a my electrician when I will see him next monday to install my dedicated 20A circuit.

    Is there an electrician or an engineer that could chime in and give us a clean answer, with reference to back him. I am a scientist, and works only with facts. Tought electricity was less "empirical".
     
  10. Chris PC

    Chris PC Producer

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    My subwoofer has two prongs polarized, no ground plug.
     
  11. RobertR

    RobertR Lead Actor

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  12. Bob-N

    Bob-N Supporting Actor

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    I work with electricity every day as a product safety engineer. I worked for UL (Underwriter's Laboratory, the UL in a circle on the back of your toaster) for 5+ years certifying products and am working at a large router company doing the same thing. Am I qualified? I think so, so here's my take on a cheater plug:

    Rick basically has it correct. The ground is there to provide a low resistance conductive path in the event of an AC short to the chassis. Internally, the ground from the wall is directly connected to the chassis. If the ground was bypassed using a cheater plug and if an AC circuit was shorted to chassis, the chassis would be at the same voltage potential (i.e. ~115V in US) as the AC circuit. Once someone touches the chassis (of course, they would also have to be touching the ground/floor), the electrical path is now somewhat complete (the body is basically a combination of resistance and capacitance) to ground and therefore, the person will be shocked as the conductive path to ground.

    The severity of the shock will depend on the "wetness" of their skin, how insulated they are from "ground/floor" and where they contact the "live" chassis.

    Regarding the ability of the breaker/fuse to open in this short circuit condition, it may not open due to the bodily factors noted above. The body is not a low resistance path (not as a good ground/chassis connection) and the current flow may not be enough to blow the breaker/fuse before the person is hurt.

    Now, how likely is it that someone could get shocked/hurt? Depends (as always), but tends to be unlikely. As a part of UL certification, there are certain spacing and construction requirements that help reduce the risk of a short from AC to the chassis in various conditions. If the product is built correctly and is UL certified, it is fairly unlikely that you will get shocked if you bypass the ground. In the event that the spacings required by UL get bypassed (mainly due to quality problems like loose wiring, wrong size standoffs, incorrect installation and the like), the backup protection is the ground connection.

    So, with that information, it's really up to you to decide if a cheater plug is worth the risk. My advice is to NEVER use a cheater plug unless you only have 2 prong wall outlets (like I do in my 1955 built house) and then make sure the loop/wire is screwed into the outlet to provide that ground connection. There is a good reason why that ground connection is there....for a catastrophic failure of spacings within the product.

    I hope this helps.

    Bob
     
  13. Holadem

    Holadem Lead Actor

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    Levesque,
    Rick has given an excellent explanation for the existence of the ground wire. THAT and nothing else is the definitive answer.
    It is not because you have never had a car accident that your insurance is useless.
    The kind of currents that will trip your circuit breaker (20A) are 20 X larger than what will kill you. To rely on the circuit breaker to provide protection is extremely absurd. How did they get the 20A that made them trip? through your body.
    There are gazillions of ways a bare wire could come in contact with the case of the gear, irrespective of the reliability of solid state devices.
    Perhaps there are still empirical areas in electricity. This isn't one of them.
    [EDIT] Well, Bob took the words right out of my mouth! Funny you should mention UL, my designs have to conform to CSA standards. I am dealing with spacing requirements on a PCB as we speak and they are a freaking pain in the ass [​IMG]
    --
    Holadem
     
  14. Blake R

    Blake R Stunt Coordinator

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    A circuit breaker will provide "personnel protection" under short circuit conditions. It will not save someone from a high impedance ground fault. That is what ground fault protection devices are for. The much lower ground currents associated with high impedance faults (like those through human beings to ground) will not trip/melt standard overcurrent devices like circuit breakers or fuses in most cases.
    One note about circuit breakers. The handle rating tells you little about the trip characteristics of the device. A 20 amp breaker pulling a 21 amp load might take days possibly even weeks to trip under overload conditions. Overcurrent devices must be selected to provide ground fault, overload, and short circuit protection depending on the load type.
    A three prong plug simply means the equipment will either derive it's ground from the serving system, or is using that ground to ground any metal parts or enclosures that might accidentally become energized. As has been metioned already, a low impedance return path (equipment grounding conductor) will produce currents large enough to operate overcurrent devices and prevent you from "doing a little dance" as we used to say in the trade.
     
  15. Kenny Booth

    Kenny Booth Stunt Coordinator

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    Is your HT system in the bathroom? Is the floor around your HT system wet? Are you plugging in a hand drill? a hairdryer? an iron? Are you going to put it in your mouth?
    If no, then use the cheater plug and forget it.
    Otherwise we'd all be dead.
     
  16. Bob-N

    Bob-N Supporting Actor

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    [Thread fart on]

    Holadem, Heh. UL and CSA use the same bi-national standard so if you're familiar with one, you're familiar with the other. I have my board design guys trained so it's not so much of a problem anymore. Set the CAD properties/spacings and route!

    Feel free to email me off line if you have any general questions.

    [Thread fart off:b]
     
  17. Blake R

    Blake R Stunt Coordinator

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    There you go Kenny! Damn right! Every rock and roll band I was ever in carried a half a dozen of 'em(2 wire adapter) I never once saw a guitar player "cook off."
     
  18. Paul Clarke

    Paul Clarke Supporting Actor

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    Sometimes I think people worry too damn much. Next we'll be putting nets under all of the bridges. The cheater plug works, period. I don't stand in puddles and operate my A/V equipment nor do I pour cupfuls of water in and around my A/V rack. Likewise, if a 'live wire' is contacting the innards of my equipment and setting up a potential discharge to my unsuspecting 'pinkie', I'm certainly not aware of it. And why is that? Because folks, it just ain't happenin'.
     
  19. Greg_R

    Greg_R Screenwriter

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    The reason I avoid using cheater plugs has nothing to do with safety. The reason your speakers are humming is due to noise being injected into your system. Floating the ground doesn't fix the problem... it merely covers up the indicator of the problem. Your system is still receiving noise (which can't be good for it's sound quality). Find the actual problem (99% of the time it's the CATV or DSS) and fix it (as detailed in past posts)...
     
  20. Joseph_W

    Joseph_W Stunt Coordinator

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    The safe answer is to avoid cheater plugs.

    However, what is causing the hum is a ground loop which is usually caused by the shielded cables tying all the grounds of our equipment together. Hard for me to believe they will all float at 120V without a path to return.

    Also, why is my receiver OK with just two prongs. I think my Sampson amp has a middle prong because it is commercial, designed to be used under all sorts of wicked conditions, such as wet basement floors. My hairdryer and power drill run off two prongs, someone is convinced that is safe.

    Joe
     

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