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What position should ground switch be in?

#61
mr80htz said:
16 people...out of how many musicians using the same amps? Not really a convincing number. I'll tell ya what, when I'm singing at a gig I'll play my SS Ampeg B5R
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This is just a list on the internet. None of that matters.

I’ve been zapped many times in the old days. So have other people that I’ve played with. It was common.

What is important is that regulatory agencies around the world have safety requirements for equipment that have to be met in order to obtain approval for new products. Vintage amps don’t meet those requirements.

Any type of shock emparted to a user from an appliance is unacceptable.

Any measures that can be taken to make equipment safer should be taken.
 
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#62
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#63
Wasnex said:
It could mean several things. One amp may have an open ground in the power chord or plug, the wall outlet may not have a good ground, etc. IMHO, it's a good idea to find out what is wrong and have it fixed.
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I have seen three wire power cords added to amps with the ground not attached. It begs the question "Why?".

byacey said:
If the modified amp with a 3 conductor line cord is plugged into a GFI receptacle or a circuit with a GFI breaker, it'll trip the GFI and kill the circuit should the chassis cap be switched to the hot side of the line. It's best to remove the cap altogether if a 3 wire cord is used.

If the chassis ground is floating because of someone using a ground lift cheater plug, the musician inevitably becomes the shunt to ground.
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I've never seen a GFI that trips at 3.5 microamps (roughly the current through .047 uf at 60 Hz). Typical GFI trip currents are 1000 times higher.

There's no need to disconnect the ground cap and switch. The cap is never "shorted out" in a 3 wire circuit. There is a need to make sure the third wire on the power cord is connected to the chassis. Ground is one of the things that the NEC (National Electrical Code) is stringent about, for safety reasons. The OP has already found this out. The shock is from the chassis floating up to about 1/2 the line voltage through the interwinding capacitance of the power transformer. It's not the full power line current or voltage, which would knock them across the room, or worse. The ground switch & cap counteracts that in a two wire circuit, and the chassis ground wire eliminates it in a 3 wire circuit.

OP, get the amp wiring checked, so you know you don't have something else wrong in there that might actually hurt you.
 
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#64
byacey said:
The author of that page doesn't seem to understand the definition of electrocute means dead. No revival. In that context it's amusing to read so and so was electrocuted, but after a few minutes they were feeling better.:D
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I'm sure that Keith Richards has been killed several times. He's like a zombie.

This definition of electrocution is "to kill or severely injure by electric shock" (Definition of ELECTROCUTE).
 
#66
okcrum said:
I have seen three wire power cords added to amps with the ground not attached. It begs the question "Why?".



I've never seen a GFI that trips at 3.5 microamps (roughly the current through .047 uf at 60 Hz). Typical GFI trip currents are 1000 times higher.

There's no need to disconnect the ground cap and switch. The cap is never "shorted out" in a 3 wire circuit. There is a need to make sure the third wire on the power cord is connected to the chassis. Ground is one of the things that the NEC (National Electrical Code) is stringent about, for safety reasons. The OP has already found this out. The shock is from the chassis floating up to about 1/2 the line voltage through the interwinding capacitance of the power transformer. It's not the full power line current or voltage, which would knock them across the room, or worse. The ground switch & cap counteracts that in a two wire circuit, and the chassis ground wire eliminates it in a 3 wire circuit.

OP, get the amp wiring checked, so you know you don't have something else wrong in there that might actually hurt you.
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You might want to check your calculations. Xc of a .047mfd @ 60Hz is 56,438 ohms. 120V RMS / 56,438 = .0021 ma (milliamps). 2ma will certainly trip a proper functioning GFI.

That would make a good epitaph: "Whoops! He had the decimal in the wrong place."
 
#69
BassmanPaul said:
There is an old saying that you can lead a horse to water but you cannot make it drink. At least I tried to steer the OP to a path for his safety. Maybe that there horse should have been a mule!! :rollno:

Electrocution is fatal period! An electric shock is called electrocussion.
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Thank you for your numerous comments. Very helpful for sure. I mentioned somewhere in these posts that i will be taking it to a tech to get it fixed just to be safe. The original questions, as well as subsequent ones, was just trying to understand how to use my amp properly and figure out it there is a serious issue. There doesn't seem to be a consensus on the latter. Either way, questions answers and a tech will make a few $$ of me. Thanks again for the comments. :)
 
#71
byacey said:
You might want to check your calculations. Xc of a .047mfd @ 60Hz is 56,438 ohms. 120V RMS / 56,438 = .0021 ma (milliamps). 2ma will certainly trip a proper functioning GFI.

That would make a good epitaph: "Whoops! He had the decimal in the wrong place."
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Yep. Thanks for the correction. So, don't plug it in near the pool or in the venue bathroom. ;)
 

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