The evil 2 prong plug.

[tap4154]

Of course the outlet could still have the neutral and hot wires switched, or elsewhere in the building as well. But if you have a 3-prong cord (and the outlet is sctually grounded... I've seen 3-prong outlets installed with no ground wire attached, and the box was isolated as well), at least you aren't the only path for electricity to travel to ground if your strings have voltage going to them, and you touch grounded metal like a mic or faucet etc.

 

[telex76]

yeah its a shame all the guitar players from the 50's and 60's were electrocuted. There might have been some good music.

 

[tap4154]

Hey, was was shocked all the time in the 70's by my Champ Amp. Fortunately, I was never grounded, just stung by the strings a bit, so I didn't die, and wasn't a good player anyway.... so.

But IMO it's just dumb not to update your vintage amp. Not just for safety, but for less hum.

No laws against being dumb in America, so feel free to keep them stock ;o)

 

[Birdmankustomz]

The idiot I bought my 60 watt tube head from ripped the ground prong out of the plug. I'm thinking I'll just put in a socket so I can use removable cords in the future.

 

[jefrs]

I live in China and bought a Roland Cube 30x locally which has only a 2 pronged plug. From what I'm reading, this is pretty dangerous, right? But honestly I don't trust any electricians in this country, I'll probably just buy a new amp if it's that dangerous.

The Roland CubeNNX are 'double-insulated' (concentric box symbol) plus they are solid-state (low voltage) which allegedly makes them safe. Not!

Double-Earthed only applies to equipment where you cannot touch the chassis. The CubeNNX chassis can be touched, it is the outer of the input jack i.e. your guitar strings, and the top/back panel is metal. The concentric box (to the RHS of "Roland" on the rear model label) marking is in error and a matter for the trading standards safety people.

Once you have had a shock from an amp, you will never, never, never use an old 2-pin one or one without an earth. I also recommend using an RCD circuit-breaker on all systems at all times, it can kill the power before it kills you.

It may not be the amp that goes wrong but other equipment but you want to dump charge through an appliance, not you.

I got a 3-wire fitted to my Cube20X, plus the chassis earthed (and it's quieter too).
This is very easy to do with some pukka 3-conductor mains flex on your country's 3-pin plug, two spade connectors and an earth eyelet tag-washer.

 

[tap4154]

Now if I did everything exactly the same as above, but only used 14-2 and no bare ground in the romex covering and hooked a jumper from a ground screw to a neutral, is that not the same circuit and earth grounded?

This is actually more dangerous than leaving it non-grounded. It's called a "false ground".

Info
http://www.inspectapedia.com/electric/False_Grounding.htm

 

[Mark F]

Thanks for the "This!", but it really wasn't a rhetorical question.

I really do want to know: Will I be okay with my amp on a 2-prong cord as long as as it's plugged the "right way" into a polarized outlet? Do I have to make sure that EVERYTHING I touch while holding my guitar (like my multi-effects pedal, mic, etc.) is also plugged in the same way?

Missed this Jupiter, sorry...

You will be much better off making sure your amp is plugged in 'the right way', and also making sure everything is plugged in 'the right way' that's in your chain.

Just wondering, do the plugs over there have fuses inside?

 

[Agave_Blue]

Found on another forum, but probably worth repeating here:

With more folks discovering the joys of a tube amp. and some finding a little bundle of tube joy at garage sales, pawn shops etc., It's essential to know that older amps that have a two prong power cord, can be quite dangerous. Even those that have been fitted with a 3 prong power cord, that came with a 2 prong cord in it's original state, may not be wired to modern standards correctly.

Most tube amp folks know this, but some may not. Hence this post.

I'm no expert on which amps had this configuration, but most older Fenders do, and I'm sure many others.

For those that have an older amp. it would be wise to check out the power wire circuit, or if you're not used to working inside an amp, have an amp tech do it for you.

Referring to the illustration below, you can see that if the death cap fails, and they all do at some point, then the power shorts to ground, ( Chassis), and guess where the ground path lies? Through your guitar cord, through your strings, and then through you!

This is not meant to scare folks away from a sweet old amp, but to make some folks aware that a possible hazard exists.

I'm sure that some of the hard core amp guys here will chime in and offer more info, but amp makers were more concerned with protecting the amp in times past, than protecting the player!

So buy that old amp. Play it like you stole it, but know what you have, and be safe with it.

Cheers! :thumb:

Worth repeating: Just because your vintage amp has a 3-prong cable, doesn't mean it's wired safely!

And: There is no good reason, outside of museum pieces, to leave the original wiring scheme in place. If the amp gets used, the power supply should be rewired. In my opinion. :laugh2:

Here's a nice graphic layout of the Fender circuit, along with simple instructions that even my puny mind could follow: Install - 3 Prong Power Cord on a Vintage Fender Amp | Guitar Files(TM)

I was even able to reuse the original wiring, and had a nice piece left over after the conversion, too!

image removed

http://www.mylespaul.com/forums/squawk-box/103068-death-cap-2-prong-power-cords-caution.html

 

[Jupiter]

Just wondering, do the plugs over there have fuses inside?

I don't think so, but I don't really know what a plug with a fuse would look like; the plugs here look exactly the same to me as (2 prong) plugs in the US, and I've never had one cook off, so I'm guessing not.

 

[Guitar_Ninja]

Any large appliance or device in Japan which requires a ground will have a special plug connected to it with a copper plate on the bottom which then fits into a special grounded outlet. You screw it down into the outlet and voila, there's your ground. Everything else is double insulated.

Most newer homes there should have these special outlets installed in say the kitchen for the fridge, the living room for the air conditioner, etc. If not then you need to get one installed.

Does seem odd not to have a ground plug, seeing as how the voltage there is only 100V. Much higher current running through those lines than Europe, or even North America.

As far as amps go, nothing is safer than keeping the chassis at ground potential.

 

[Mark F]

I don't think so, but I don't really know what a plug with a fuse would look like; the plugs here look exactly the same to me as (2 prong) plugs in the US, and I've never had one cook off, so I'm guessing not.

If there is no fuse in the plug, your relying on the breaker/fuse at the board.

If you can, i'd definately get a grounded socket installed (as Ninja says)

And definately check everything is plugged in the right way until then

 

[fly135]

Also, most buildings in Japan have no real earth electrode. It's less expensive to double insulate appliances than to overhaul the electrical system used in the whole country (though they could 'phase' grounding in if they thought it necessary)

if they don't tie either side to ground then the person won't be grounded.

 

[Mark F]

if they don't tie either side to ground then the person won't be grounded.

there are circumstances where the person could be at a different potential to the live, all depends on things like where someones playing, the building structure, or anything they touch with guitar in hand. If the polarity is kept correct, there probably wouldn't be a problem, but there's a reason most countries have moved over to having earthing systems. Japan has gone in a different direction, and as i've said, without knowing the ins and outs i'd at least recommend keeping correct polarity, with a possibility of having a grounded socket fitted (which seems to be happening slowly in Japan given other posts). That's just me though...

 

[DenisS]

A 3-prong A.C. cable gets added to every old Fender I work on.

But then other things are necessary.

1 - Resequence the power path to put the switch ahead of the fuse so that when you replace the fuse you are not dealing with a live fuse-holder.

2 - Make the neutral go directly to the power transformer (to the white if you have one on your transformer). Also to the courtesy outlet silver screw.

3 - Add a center-off polarity switch with a safety cap to chassis, so that if the wall outlet is wired wrong you can take your polarity switch out of the center position and set it to the side that gives less hum when you buzz the amp through your guitar cable with your hand at low volume.

Now you have a hard ground, and if the wall is wired wrong you have a cap-coupled neutral to chassis like an old amp that is plugged-in correctly.

The safety cap is good, but the standard old cap will work fine. Safety caps fail by opening-up instead of shorting out. That may rarely happen, but it's safety.

 

[Scotty 2]

Eric Johnson is the same guy who is positively convinced he can hear the difference if the guitar's cord is turned around and plugged in the other way.

Right. That's what I said too.

Not to bash the guy, but he's plainly delusional. I think he needs to be medicated. Hopefully before he gets electrocuted.
--Rob

Can Eric also tell a differance in tone when
right hand vrs,left hand playing guitar? That's splittin them
straws pretty fine,isn't it?

 

[Tele-Champ]

All of us here who have experienced that fabulous "lip toaster" feeling when contacting a microphone that is 120VAC relative to you, please yell "AAGGGHHH!".

Count me in. It's not something you want to experience.

+1. Not fun. Have had it happen once or twice to me. Kind of ruins a jam.

 

[rainedave]

From a 1950's Fender amp manual:

"If when the amplifier is first turned on one experiences a slight hum more commonly known as line noise and if the amplifier pops or crackles when the metal parts or strings of the instrument are touched, it is an indication that the A.C. plug is improperly polarized; to rectify this condition, it is only necessary to remove the 110 volt A.C. plug from the socket, rotate one-half turn, and re-insert the plug. The amplifier is then properly grounded and will cause no more difficulty."

 

[jh45gun]

From a 1950's Fender amp manual:

"If when the amplifier is first turned on one experiences a slight hum more commonly known as line noise and if the amplifier pops or crackles when the metal parts or strings of the instrument are touched, it is an indication that the A.C. plug is improperly polarized; to rectify this condition, it is only necessary to remove the 110 volt A.C. plug from the socket, rotate one-half turn, and re-insert the plug. The amplifier is then properly grounded and will cause no more difficulty."

Which is what my tech believes in. I figure you can always put a voltage meter on the chassis and the mic stand to make absolutely sure.

telex76 yeah its a shame all the guitar players from the 50's and 60's were electrocuted. There might have been some good music.

Yea I been shocked more than a time or two but nothing major. I always just checked the plug for the proper polarity and made sure the PA was plugged in the same way.

Though most of my stuff all has three prong plugs now you still can use a two prong if you know what your doing and you check the circuits of the places you play with a circuit tester.

 

[65flh5326]

"A 3-prong A.C. cable gets added to every old Fender I work on."

Well you aint working on my old Fender amps!

"Though most of my stuff all has three prong plugs now you still can use a two prong if you know what your doing and you check the circuits of the places you play with a circuit tester."

A voice of reason?

Maybe I am getting sick and tired of arm chair heroes trying to save me from myself!

 

[tap4154]

From a 1950's Fender amp manual:

"If when the amplifier is first turned on one experiences a slight hum more commonly known as line noise and if the amplifier pops or crackles when the metal parts or strings of the instrument are touched, it is an indication that the A.C. plug is improperly polarized; to rectify this condition, it is only necessary to remove the 110 volt A.C. plug from the socket, rotate one-half turn, and re-insert the plug. The amplifier is then properly grounded and will cause no more difficulty."

Hey, in 1950 even doctors endorsed smoking cigarettes on TV and in print ads. We learn and adapt all the time. But if folks want to live in the past out of some superstition that not having a properly-grounded amp will improve their tone, that's fine by me. I frankly don't care if you buckle your seatbelt either, if you think it makes you drive better ;o)