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In Reply to: RE: Fuse Holder posted by Chip647 on June 06, 2016 at 05:24:28
Wouldn't safe practice have the terminal at the right or "tail end" connected to the hot line?
Follow Ups:
"Wouldn't safe practice have the terminal at the right or "tail end" connected to the hot line?"
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Buy Chinese. Bury freedom.
Stupidity notwithstanding by attempting to replace a fuse while the equipment is plugged in, I'll quote a response from another forum:"connect the incoming voltage to the side contact. Then, when the user fits the replacement fuse and pushes it into the fuse holder and it makes contact with the spring at the end, the fuse will not be live and he will not get a shock. The live part makes contact with the metal on the inside of the screw-on cover, and that's insulated, so you can't touch it."
Edits: 06/09/16
"when the user fits the replacement fuse and pushes it into the fuse holder and it makes contact with the spring at the end, the fuse will not be live and he will not get a shock. "
Is that a forum for Darwin Award hopefuls? The user is supposed to unplug the equipment when inspecting or replacing fuses. If he intentionally disregards that step, he should be smart enough to put the fuse into the cap, then push and twist the cap into the holder without touching the fuse. Anyone failing to observe either of those steps gets my vote.
FWIW, the reason I personally connect the tail of the holder to AC-hot is that sometimes, when the cap is twisted off, the blown fuse stays in the body of the holder. If the user forgets to unplug the equipment, the bare end of the fuse won't be hot. Of course, this only works if the fuse is blown, so it's not intended as a substitute for unplugging the line cord. It's just one more precaution that might save someone's life.
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Buy Chinese. Bury freedom.
> > Is that a forum for Darwin Award hopefuls? The user is supposed to unplug the equipment when inspecting or replacing fuses. If he intentionally disregards that step, he should be smart enough to put the fuse into the cap, then push and twist the cap into the holder without touching the fuse. Anyone failing to observe either of those steps gets my vote. < <
I agree 100%
...The assertion that contact with the fuse end caps can only occur at the end of the holder is wrong too. Every common cartridge fuse holder I examined does not prevent contact with the side contact barrel as the fuse is inserted so that supposed safety feature doesn't really exist in real life. It's also possible to contact the side conductor barrel with a finger with the fuse holder cap removed but the end contact can't be reached by most human fingers.
As already noted, the only really safe manner of replacing one of these fuses is with the cord unplugged but if one chooses to tempt fate..........
I always hook the AC cord to the rear of the fuse holder because the hole is larger and can accommodate the cord much more easily.Now that's a good enough reason.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Who knew it made a difference, after all, the fuse is the same on both ends.
I know,that is what's so nuts about it.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
A fuse HAS polarity. But, you need to gain its trust before it will tell you which side is which!
8^)
Right on LOL.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
With the fuse in tact, both of the tags are going to be hot regardless. If the fuse blows one is hot, then you unplug it. If touch safety is a concern, both should be heat-shrinked. However, you are talking about an environment where there is exposed voltage everywhere so that is kind of like wearing a 1 inch square bulletproof vest.
Standard engineering practice is to run the line or hot lead to the rear of the fuse holder.
The reason is that when the fuse is removed, the exposed front ring terminal is not hot. This is to protect the end user.
Once the chassis is open, all bets are off although many do insulate the internal connections as well.
I always put the switch first before the fuse to keep everything dead if I am too lazy to unplug. I can't imagine changing a fuse on a hot piece of equipment, but it probably is an every day occurrence.
Chip647 is absolutely right, put the switch first, much more important than which of the two terminals the hot (make sure it is hot and not neutral) is connected to. The only time I've been shocked, working on this stuff for 20 years, is when I turned an amp off, and changed a fuse when the fuse was first (DUH). Sometimes you take a shortcut when thinking (amp off), this practice helps some.
twystd
and hot to the tail end cause it is further away from stuff like the chassis that could touch the terminal closest to the cap. is easy enough to unplug before working on stuff...neglect that, and your thought process pours chlorine into the gene pool.
Switch failure would then pop the fuse, and hopefully not deliver a resistive heating process that results in an acute thermal event...LOL
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
You can still complete the circuit with your other hand when the switch is off.
"You can still complete the circuit with your other hand when the switch is off."
How? FenderLover's schematic is correct. And FWIW, you're supposed to pull the line cord before replacing a mains fuse. No amount of precautionary wiring inside an amp can substitute for proper safety practices.
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Buy Chinese. Bury freedom.
"No amount of precautionary wiring inside an amp can substitute for proper safety practices."
That is certainly true, however there is the possibility (inevitability in my case) of a brain fart. If the fuse would have been wired after the switch I wouldn't have been shocked. Sometimes it's best to make things as idiot proof as possible, at least when it comes to safety.
twystd
The right type of power entry module can solve this problem for you. I haven't EVER been tempted to touch a metal fuse cap with the line cord plugged in. And just to cover all the bases, it is NOT safe to place the switch ahead of the fuse. Safety demands that the fuse should be the FIRST thing the hot mains wire is connected to.
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Buy Chinese. Bury freedom.
Fuses are simple and reliable. Switch contacts do get welded/arced together. I do a lot of electrical testing at work. Trust me, you don't want to bet your life on a switch or circuit breaker to actually shut of power.
So yes, fuse holder first. Fuse holders should have a line and load side. When in doubt check with the manufacturer.
When a switch arc welds itself on and the fuse is blown, it is no more dangerous than having the fuse first, in both cases if you are not smart enough to unplug the unit, there is a potential for shock when changing the fuse. The way around this is to not have an external fuse access..
What will happen if the switch arcs internally to the chassis? If you're lucky, the house breaker will blow quickly. If not, the internal green earth wire might open and you get electrocuted the next time you touch the amp. Or, maybe the earth wire stays good long enough for the wiring in the amp to catch on fire. Or the wiring in your house. Take a look at any UL equipment and you'll see that NOTHING precedes the fuse. This is what's required to protect users from defects and most mishaps.
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Buy Chinese. Bury freedom.
I don't think I'm getting this. You cannot get a shock from the fuse holder, IF the switch is off. If the switch is on... you can get a shock from the fuse holder, no matter if it's before or after the switch.If you are touching both the neutral and hot lines, you will get a shock. I'm wondering if the OP got a shock from the residual charge in the main PSU caps. This can happen no matter what position the switch is at.
Edits: 06/08/16
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