That little A/C receptacle tester....

[BurningSkies]

That sucks. It bothers me when some people are just cavalier about electrical safety. A few years ago I was working with an acoustic guitar player who had a three-prong to two-prong adapter on the plug of his amp. Both his amp and mine had DI feeds to the mixer. I told him if he uses that adapter I was going to pack up and go home because I was not going to have my cable, DI, and amp be his path to safety ground if anything went wrong in his amp. He protested that without that adapter he gets buzz but it always goes away when he lifts the safety ground. I stood my ground. I pulled the adapter off and plugged his amp in. There was no buzz.

Ironically, those adapters are actually intended for making devices safer by allowing you to plug a three-prong plug into a two-prong outlet and connect the safety ground tab or lead to the center screw.

Exactly. My old house which only had 2 prong outlets I used these regularly and screwed them in correctly as well. Of course, it didn't help since the center screw wasn't grounded either.

I do more than carry one of these testers...I have it plugged into the first spot on the power strip I use, so it's always there when I power on. Although I know that the power at the outlet is only have the equation and I can't wander around the venue testing things.

 

[cazclocker]

This thread reminds me of a solution I used to carry with me to EVERY gig. I had two pieces of gear to deal with house wiring at any venue:

1. A wiring tester, like the OP recommended.
2. A homemade 4-outlet junction box. Two of the outlets were wired normally, just the way any up-to-code outlet should be wired. The other two outlets were deliberately wired with (1) the hot and neutral reversed and (2) the ground and neutral reversed.

So the first thing I’d do at a new venue was to check the house wall outlets with my tester. If the outlets showed the hot & neutral reversed, then I’d just plug in my junction box into the incorrectly-wired outlet. A quick recheck of the outlet that also had the hot & neutral reversed would show that the problem had been rectified... sometimes, two wrongs make a right! And if the original problem with the house wiring was the ground & neutral were reversed, my junction box had an outlet for that, too.

When I built the junction box, all the wiring was heavy 12-gauge, as I recall. And the cord was short.

I lost that junction box some years ago when it was stolen. I should build another one.

 

[Rick James]

So the cause was most likely a miswired receptacle, with the hot and neutral wires reversed? And with one piece of gear plugged into the reversed outlet and another into a different (correctly wired) outlet, with a link between them via the DI line, there'd be a large potential between the two chassis?

With a 3 wire connection reversing hot and neutral, the two flat prongs, won't make any difference safety wise, assuming there are no internal faults. Reversing hot and ground, the round third pin, will make the chassis ground, and anything connected to it, hot. Connect that to anything else that really is grounded and you've got a problem.
A less likely scenario is when you have very long extension cords. That can result in the ground potential at the end of the extension being quite a few volts higher than it should be, caused by the resistance in the wire between where it reaches the service ground and your rig, so two wires that are both technically grounded can still pass current between them. This is why you can get zapped when you set up outdoors and stand on a damp surface. The resistance of the total length of wire between your strings and the service ground can be considerably higher than the resistance between your strings and the damp surface, and you become the proverbial path of least resistance to ground.

 

[CryingBass]

The receptacle testers are very useful. I have a bunch of them so I can usually find one when I need it. I buy the ones with the ground fault circuit interrupter device test button on them.

There is one limitation to these testers which is the inability to detect what some people refer to as reversed hot and neutral, with a "bootleg ground". This is a condition I have encountered more than once in homes where the homeowner, or clueless handyman has reversed the hot and neutral wires, and also connected the receptacle equipment grounding terminal to the incorrectly connected neutral wire.

Here is a website with a diagram that illustrates it better than my written description: Failures in Outlet Testing Exposed which also shows a more reliable way to test for this fault using a quality medium sensitivity non-contact voltage detector on the grounding terminal of a receptacle. Very well written article.

One way to test for wiring errors in receptacles on different circuits that are some distance apart is to connect a three wire extension cord into one receptacle, and use an AC voltmeter at the other receptacle to see if any substantial voltage, (more than maybe 6 VAC) exists when putting the meter leads between the two grounding lugs. Likewise the neutrals should not have much difference. And a meter reading between neutral and ground should not show much voltage between them. You might see a difference of a few, or as much as 240 VAC measured between the two hots, depending on which phase of the power it is connected to in the panel.

If you see something like thirty or forty volts between grounds or neutrals even if you don't burn something up or get a shock, you might have problems with 60 Hz noise. If you do this test with a load like a lamp plugged into one or both circuits and you see a big difference, don't connect any of your equipment to either circuit until the fault is rectified.

I am not a licensed electrician, but I have independently studied the coursework that my local community college uses to train electricians. And I have been an electronics technician, and field service engineer in very high-tech and industrial environments for over forty years. Anyone who knows me, calls me whenever they need electrical work. And I have installed numerous service entrances and done residential, and commercial electrical work with permits and inspections, and have never failed an inspection.

I started taking photos of very dangerous electrical installations that I have found, and some of them are shocking! Pun intended. I have found wiring blunders that were like a trap waiting to kill someone. I quit photographing them because there were so many of them. I have found poor workmanship resulting in installations that were actually smoldering, and likely within hours of starting a fire in someone's home on two occasions. One the result of improper repair work on aluminum wiring, and another involving a loose connection resulting in heat buildup due to unintentional resistance at the connection point to the wiring device.

It is amazing how much unsafe wiring is out there.

That link to the testing article itself could save many TB lives here. I never new 1/2 of that. Thanks Hooch!

 

[2tonic]

This whole thread is a solid reminder of why you should check not only the AC supply at every venue, but also every signal cable for proper polarity/continuity.
This can be easily done with either a volt/ohmmeter (hell, they give them away free down at the Harbor Freight store) or a dedicated tester. There are several multi-function units on the market that test XLR and 1/4" cables, as well as phantom power voltages and buss fuse continuity by simply inserting one or both ends in the tester.
Your life ( and your gear) is worth spending a few dollars to protect.
Glad the OP wasn't injured, other than just financially.

 

[Gaolee]

I do more than carry one of these testers...I have it plugged into the first spot on the power strip I use, so it's always there when I power on. Although I know that the power at the outlet is only have the equation and I can't wander around the venue testing things.

That's an outstanding idea. I think I'll steal it. Plagiarism is basic to all culture.

I use one fairly regularly, but forget it often enough that it could be a problem. Permanent placement on the power strip I always carry solves the non-use problem.

 

[Spidey2112]

I will never understand why somebody doesn't sell a cheap Woodhead and a Wiggy in one little device.

(If you know both of those terms yer my people. )

I'm not sure if our terms match, but I dated both in high school, and ended up marrying their aunt...

 

[tlc1976]

Ironically, those adapters are actually intended for making devices safer by allowing you to plug a three-prong plug into a two-prong outlet and connect the safety ground tab or lead to the center screw.

All my 41 years and I've seen more of those adapters than I can count, but never once seen the ground tab connected to anything. I'm sure I'm guilty of it too, and I've got some I've collected in a box somewhere, but I can't remember the last time I actually used one. (EDIT I used to plug a work light into an extension cord, I'd have to move it at its base or I'd get shocked, but the rest of it was usually too hot anyway.) I've had grounding issues, like in my college dorm when I'd get shocked from muting the strings and grabbing the steel door/handle. Changing the vintage 2 prong Ampeg cord to a case-grounded 3 prong fixed that. And my feet used to get shocked at the old house every time someone would deep clean the carpets and I'd play barefoot, for a few days until the carpet totally dried out.

I've had one of the OP's testers for probably 15 years, but I only used it for testing outlets at campgrounds, since I found out about it on an RV forum. It stays in the camper. Never once thought to bring it in the house and see what was up with my wiring.

 

[briandavismurph]

Played a live radio show last night. The event is a volunteer event where gifts for underprivileged folks are wrapped. I have played it for many years and this year we were in a new venue....and that is where the trouble starts.

I arrived and the sound man for the radio station asked what I needed to get hooked up. I told him I just needed power and that he could plug in to the D.I. on my Aguilar AG 700. So he brings me power from an extension cord and I power up my amp and it is working fine until he plugs into the D.I.! Sparks...smoke..and a blown AG 700 and a blown Mackie Mixer (the radio station's mixer). Great.

I went to my car and retrieved my back up head..Genz Benz Shuttle 9.2. Plug it in but then thought about that little receptacle tester in my bag...plugged in the tester and it showed the power was wired wrong!

Got extension cords and ran power from a correctly wired receptacle and thought all was right. My amp powered up fine and sounded good. Then the sound guy went to plug in to the D.I. and again I see sparks fly! The Shuttle was still working but I had fears about the D.I. being damaged. Played the gig and came home and checked the Shuttle and, sure enough, the D.I. is damaged.

The radio station is going to pay for the repairs but, man, I sure wish I had used that little receptacle tester before I turned on my Aguilar.

This is a link to the tester.

https://www.amazon.com/Electrical-Receptacle-Outlet-Ground-Tester/dp/B0012DHVQ0

Get one and use it EVERY time you go to a new venue.

On a similar note we were at a gig where our power supply was on a dimmer, yielding 80 volts or so, the amps powered up but all had unintended "fuzz tone". Finally figured it out, turned up to full power and problem solved.

 

[agedhorse]

Ironically, those adapters are actually intended for making devices safer by allowing you to plug a three-prong plug into a two-prong outlet and connect the safety ground tab or lead to the center screw.

Which only works whe there is a ground connection to the box/device yoke... not too common on knob & tube wiring systems

 

[agedhorse]

Reversing the neutral and hot on a 120V cat) does not matter safety-wise (though it's a terrible practice)

Of course on 120/240V and 120/208V 3 phase wye it would be disasterous.

 

[Hoochie Coochie Man]

briandavismurph said: "On a similar note we were at a gig where our power supply was on a dimmer, yielding 80 volts or so, the amps powered up but all had unintended "fuzz tone". Finally figured it out, turned up to full power and problem solved."

Controlling a standard receptacle by a dimmer is prohibited by NFPA 70, Article 404.14(E).

A dimmer listed for the purpose would be allowed, and there is such a thing as a receptacle controlled by a dimmer, but a standard nema plug won't fit it. Lurton makes it, and supplies a two wire plug that can be attached to lamp cord.

 

[two fingers]

I'm not sure if our terms match, but I dated both in high school, and ended up marrying their aunt...

Woodhead

Wiggy

The Wiggy just lights up a bulb by the proper voltage measured. But you shouldn't need probes with a 2n1 device because blades are already in the receptacle from the Woodhead.

 

[jnewmark]

Good stuff. I guess my question would be : You get to the gig and test all the outlets on stage, and they are all wired incorrectly. What do you do ?

 

[Hoochie Coochie Man]

Which only works whe there is a ground connection to the box/device yoke... not too common on knob & tube wiring systems

I have seen work done where it was apparent that someone thought the aluminum bonding wire inside the flexible metal sheath of two wire type AC, (armored cable) was an acceptable equipment grounding conductor and so tried to ground a metal box by winding it around a wood screw that attached the metal box to a wall stud or wood bracket.

 

[xnewyorka]

This thread reminds me of a solution I used to carry with me to EVERY gig. I had two pieces of gear to deal with house wiring at any venue:

2. A homemade 4-outlet junction box. Two of the outlets were wired normally, just the way any up-to-code outlet should be wired. The other two outlets were deliberately wired with (1) the hot and neutral reversed and (2) the ground and neutral reversed.

That right there is pure genius at work.

I lost that junction box some years ago when it was stolen. I should build another one.

And the person who ran off with it with it may well have tried using it and paid a fair price for the five-finger discount.

 

[xnewyorka]

Good stuff. I guess my question would be : You get to the gig and test all the outlets on stage, and they are all wired incorrectly. What do you do ?

Simple - you play left handed with your bass upside down and your back to the audience!

And if you are serious enough to have a contract for the gig, you make sure that every contract includes a clause that the venue will supply power that conforms to all applicable local and national electrical codes.

And if you are really serious, you tell the club that tonight is a special night - your band will be playing raw and unplugged, so everybody better cozy up nice and close to the stage!

 

[DigitalMan]

All this reminds me, even though I’m not playing out anymore, that every show I’ve done since the early 90’s has been with a wireless unit. As an occasional backup vocalist, I can attest that electricity tastes bad.

 

[agedhorse]

That right there is pure genius at work.

And the person who ran off with it with it may well have tried using it and paid a fair price for the five-finger discount.

It's actually pretty scary that somebody thought this was a good idea...

 

[xk49w]

. . . I do more than carry one of these testers...I have it plugged into the first spot on the power strip I use, so it's always there when I power on. Although I know that the power at the outlet is only have the equation and I can't wander around the venue testing things.

Good idea. I wonder if there are power strips with the detector built in? If one has to use a power strip (and who doesn't), maybe one with a GFI would be good thing.