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No Ground causing shocking results

J

jwb39

Jun 2, 2008
52
10
Dover, Oh
#1
So, this guitarist that I frequently play with bought an old west tube combo *guitar* amp and it only has a two prong connector. It shocks everything. If he touches a mic, he gets shocked. If anyone touches him, they get shocked. After getting shocked three times during a jam session, I've had enough.

What do you need to do to ground the amp? Do you need to get a three prong plug and connect the ground plug to the ground on the amp or is it more complicated than that? I've had some experience building pedals and wiring electronics, but is there anything inside the amp that I should be afraid of?
 
#5
I offer this link to a how-to on grounding a fender amp, because you can find it yourself with a simple search.

Two notes:

1) As it says in the article, if you have to ask how to do this, you probably should not be doing it yourself.

2) Not all amps are built same as Fender - so no guarantees that this is correct for the amp in question.

BUT - GET IT GROUNDED!! It's not expensive and it's extremely important.

Install 3 Prong Power Cord On A Vintage Fender Amp | Amp Tech | Guitar Files(TM)

Here's another link to a similar question...same cautions apply...

Invalid Link Removed

I'm decently handy with electronics and soldering, but I paid a tech to do this for my old blackface Bassman amp. I considered it cheap insurance.
 
#8
I'm no expert, but I had a similar problem today. Recently my rig has been shocking me too, the static was so bad I got shocked when I touched the bass strings. The thing is I used a furman power conditioner, and that was what was causing the problem. Changed the power cord from a 2-pin to 3-pin (grounded), solved my problem. But yeah I would suggest taking it to a proper technician though.
 
#9
Wiki says: It is sometimes suggested that human lethality is most common with alternating current at 100–250 volts; however, death has occurred below this range, with supplies as low as 32 volts. Typical tube amps can run 350-450 volts DC. Yikes!
 
#10
Have a read:

Electric shock - Wikipedia, the free encyclopedia

The minimum current a human can feel depends on the current type (AC or DC) and frequency. A person can feel at least 1 mA (rms) of AC at 60 Hz, while at least 5 mA for DC. The current may, if it is high enough, cause tissue damage or fibrillation which leads to cardiac arrest. 60 mA of AC (rms, 60 Hz) or 300–500 mA of DC can cause fibrillation.[2][3] A sustained electric shock from AC at 120 V, 60 Hz is an especially dangerous source of ventricular fibrillation because it usually exceeds the let-go threshold, while not delivering enough initial energy to propel the person away from the source. However, the potential seriousness of the shock depends on paths through the body that the currents take.[2]
Click to expand...

Note that 120 V, 60 Hz is exactly what your amp is getting from the wall. Get that thing fixed professionally ASAP, and DO NOT use it until that happens.
 
#11
My old YBA1a used to give me the shocks quite often. My hair still won't comb right.
It shuoldn't cost more than $35 or so to put a 3 pronger on that amp. If it's that bad in your jam space, I hate to imagine how bad it will be when you take it out to a dive bar or some other venue. Especially when the house sound is on a totally different circuit. Then you step up to the mic and get blue flashes.
I've done this before! Not fun!
 
#14
gnjpowell said:
Wiki says: It is sometimes suggested that human lethality is most common with alternating current at 100–250 volts; however, death has occurred below this range, with supplies as low as 32 volts. Typical tube amps can run 350-450 volts DC. Yikes!
Click to expand...

It ain't the voltage that kills you, it's the current. I've been shocked by over 50,000 volts on purpose, just for the fun of it. But the source had almost no current capacity. I've also been shocked accidentally by 440 volts DC. It knocked me half-way across the room.
 
#15
Pilgrim I just read the article you posted and I have to disagree with one thing in it. Do not run a wire from the fuse holder to the ground switch. That's just asking for trouble run the wire from the fuse holder straight to the convenience outlet. just wanted to point that out because if somebody attempts this and grabs the wrong terminal with the ground wire then they will have a direct short from hot to ground...and they will be in the dark when they plug it in:) When ever you rewire an old amp the very first thing that the black (hot) wire should hit is the fuse holder.
 
#16
billfitzmaurice said:
Only lethal voltages. Have a tech bring his amp up to code. While he's at it install one of these:
[Invalid or Expired Link Removed]
Click to expand...

Hey, I was looking for one of those! I have a dinky little 15W crate guitar amp that needs the cord replaced (ground is broken off), and figured I'd upgrade it to one of those.
 
#17
Everybody in this thread is jumping to conclusions! Take a deep breath and slow down.

1. Is the guitar player any good?
2. How hot is his girlfriend/wife and does she like you?
2. Does he have any cool stuff you could get if he died?

You have to consider these things before rushing off to the tech to get that amp fixed.
 

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