The word on AC mains switch/fusing

[Smokebreak]

Which do you prefer and why-

Hot>fuse>switch>pt and neutral>pt

Or

Hot>switch>pt and neutral>fuse>pt

Or otherwise? I haven't had a problem with either but surely one must be more effective in meltdown situations?

[Randall]

First one is how I like to do it. Seems a better idea to me to disconnect hot at the first possible opportunity upon entering the chassis. The other way could possibly leave you with a partially energized PT maybe getting it's return from a leak somewhere. Or at the least, with the hot potential on the primary of the PT, looking for a way home.

[Smokebreak]

Me too, but isn't there as much electricity on the "cold" side to present problems if not protected?

[JazzGuitarGimp]

In the US, the cold side (neutral) is supposed to be at the same voltage as ground. So if you have a popped fuse on the hot side, there is no dangerous voltage sitting on the cold side of the PT, looking for a return path.

[VacuumVoodoo]

In the US, the cold side (neutral) is supposed to be at the same voltage as ground. So if you have a popped fuse on the hot side, there is no dangerous voltage sitting on the cold side of the PT, looking for a return path.

But this assumes the power outlet you plug into is wired correctly. What guarantee is there that it is?

[ToneMerc]

Which do you prefer and why-

Hot>fuse>switch>pt and neutral>pt

Or

Hot>switch>pt and neutral>fuse>pt

Or otherwise? I haven't had a problem with either but surely one must be more effective in meltdown situations?

There's only one correct way to do it PERIOD!, which is to fuse the hot side. I see so many clones and some kits that are just plain wrong. Just because Fender or Marshall did it that way 50 years ago doesn't make it right in 2013.

It's never a problem until someone is shocked or there's a fire. In 2013, pleading ignorant will be a poor defense in a lawsuit.

TM

[Guus]

Hi Smokebreak,

For safety and conveniance, take the first one.
Right order is: Hot(mains) - fuse - switch - PT.

Why?
If you put the fuse after the switch and you have a bad problem with the switch or switch wiring, it won't blow the fuse of the amp but the fuse somewhere in the house and so it would switch of also other things like lights, fridge with beer, etc.

regards
Guss

[martin manning]

...it won't blow the fuse of the amp but the fuse somewhere in the house and so it would switch of also other things like lights, fridge with beer, etc.

I see you know what is important, Guss!

[JazzGuitarGimp]

In the US, the cold side (neutral) is supposed to be at the same voltage as ground. So if you have a popped fuse on the hot side, there is no dangerous voltage sitting on the cold side of the PT, looking for a return path.

But this assumes the power outlet you plug into is wired correctly. What guarantee is there that it is?

So add a second fuse in the neutral circuit, just in case. Or go to the hardware store and spend a couple bucks on one of those three-light, plug-in, circuit-testing thingamajiggies and use it faithfully at all your gigs. Or, wear both a belt AND suspenders!

[NickC]

....... three-light, plug-in, circuit-testing thingamajiggies and use it faithfully at all your gigs ........

I've been doing that for over 30 years now. It's shocking (no pun intended) how many dive bars / clubs have bad wiring. I've fixed quite a few dangerously bad situations and told the owner it's a "value added service", since it saves him the burial costs of electrocuted musicians.

[Phil_S]

Just apply a bit of logic and knowledge of what's safe and you'll quickly see there is only one way to do this.

Let's set aside bars that have the hot and neutral reversed (for that you MUST carry a tester and use it every time, even in places you played before.)

The only thing that makes sense is to fuse the hot side and it HAS to be before the switch. That way, as soon as you plug the amp into the wall socket, the fuse is energized and doing it's job. If you put the fuse after the switch, you have defeated one of the primary benefits of using a fuse. BTW, that fuse is there first to protect the building from the amp and second to protect the amp.

Returning to the bar with a bad wiring job, it certainly doesn't hurt to fuse both the hot and the neutral. I'm not an electrician, but it's my understanding that fuses on both legs isn't required in the US; I don't know about EU. I believe in the EU, you are required to switch both legs of the wall connection to the PT primary, which is why you will see a double throw switch used and this certainly couldn't hurt even in the US.

[vibratoking]

Yup, fuse the hot before the switch.

Bring a checker and use it. I rigged up a fixer, which is a junction box with switches so that I don't have to fix the 'venue'. It plugs into the 'bad' outlet and can switch the hot and ground and the neutral and hot. It's a potentially dangerous box with no built-in protection. I put a lid on it so the switches can't accidentally be toggled. If my fixer can't fix the problem, I go searching for a different outlet. I am not as nice a Nick. I don't fix outlets for the 'venue'. Besides, if something goes wrong down the line and they know I monkeyed with it, then my name is brought into the situation. I let the 'venue' owner know his wiring is bad and ask him to deal with it.

[Randall]

I don't fix outlets for the 'venue'. Besides, if something goes wrong down the line and they know I monkeyed with it, then my name is brought into the situation.

^+1^

[NickC]

Yup, fuse the hot before the switch.

Bring a checker and use it. I rigged up a fixer, which is a junction box with switches so that I don't have to fix the 'venue'. It plugs into the 'bad' outlet and can switch the hot and ground and the neutral and hot. It's a potentially dangerous box with no built-in protection. I put a lid on it so the switches can't accidentally be toggled. If my fixer can't fix the problem, I go searching for a different outlet. I am not as nice a Nick. I don't fix outlets for the 'venue'. Besides, if something goes wrong down the line and they know I monkeyed with it, then my name is brought into the situation. I let the 'venue' owner know his wiring is bad and ask him to deal with it.

I like your junction box solution. Clever!

The issue became an ethical/moral dilemma for me. If I detected the hot - neutral was reversed, it was an easy fix I could do while the circuit was live in a couple minutes (super careful and know what I'm doing, but I understand that folks might consider working on live circuits to be proof I don't know what I'm doing ..... I understand that ..... but I worked on live 240V circuits too, back in the day). Or an outlet that sparks when you plug something in ...... loose connections ..... easy fix. I'd have felt guilty if I knew it was dangerous and some other band-member got hurt. The management in some of those venues would sooner send the band packing (unpaid) after driving an hour and spending the gas money, rather than fix something themselves. We'd never get gigs there again. Playing the dive-bar circuit is full of compromises. The show must go on.

There were circuits that were too messed up, and I didn't work on those. I instead ran 10 gauge extension cords from tested clean power.

[Smokebreak]

Just apply a bit of logic and knowledge of what's safe and you'll quickly see there is only one way to do this.

Let's set aside bars that have the hot and neutral reversed (for that you MUST carry a tester and use it every time, even in places you played before.)

The only thing that makes sense is to fuse the hot side and it HAS to be before the switch. That way, as soon as you plug the amp into the wall socket, the fuse is energized and doing it's job. If you put the fuse after the switch, you have defeated one of the primary benefits of using a fuse. BTW, that fuse is there first to protect the building from the amp and second to protect the amp.

Returning to the bar with a bad wiring job, it certainly doesn't hurt to fuse both the hot and the neutral. I'm not an electrician, but it's my understanding that fuses on both legs isn't required in the US; I don't know about EU. I believe in the EU, you are required to switch both legs of the wall connection to the PT primary, which is why you will see a double throw switch used and this certainly couldn't hurt even in the US.

Frankly, I never considered putting the fuse after the switch, but now that it's come up, if the idea is to shut everything down when the amp is pulling too much, wouldn't the fuse still do its job after the switch, once the switch is closed? What am I missing here?