Hi,
Iam buying this part for chassis mounting and wonder if this Bayonet Fuse Holder are safe to tube amps or is better the screw model?
4PCS SCI R3-18 Panel Mount Chassis Fuse Holder For 10x38mm Glass Fuses 30A 600V. | eBay
Iam buying this part for chassis mounting and wonder if this Bayonet Fuse Holder are safe to tube amps or is better the screw model?
4PCS SCI R3-18 Panel Mount Chassis Fuse Holder For 10x38mm Glass Fuses 30A 600V. | eBay
This option above on post 1 use a big unusual fuse.
This link below use a smaller fuse 5mm x 20mm and is screw caped to 20A 250V, my mains is 220V:
4PC SCI R3-26 Panel Mount Chassis Fuse Holder For 5x20mm Glass Fuses 10A 250V B1 | eBay
This link below use a smaller fuse 5mm x 20mm and is screw caped to 20A 250V, my mains is 220V:
4PC SCI R3-26 Panel Mount Chassis Fuse Holder For 5x20mm Glass Fuses 10A 250V B1 | eBay
The fuse carrier of this "old style" fuse holder type is not very safe and it is not recomended for CE certification. I believe that Brazil is linked to USA electrical regulation so you may still use it, but you may also check for a safer alternative.
This is a quote from the latest product catalog of a a well known producer: "Users of fuse holders designed to comply only with UL/CSA requirements are accustomed to a fuse carrier with a knurled cap that makes it easy to access and change a fuse without tools. Various international equipment standards, however, limit the degree of user accessibility to a fuse holder in order to minimize the possibility of electrical shock to a non-technical user. The limited access fuse holder is designed to require the use of a tool (usually a screwdriver). It also incorporates additional insulation and insulating barriers that eliminate the presence of live conducting services during fuse change operations."
I attack a picture of the fuse carrier style I usually see on modern equipments, I use this type of fuse holder or the one that is integrated in the IEC mains connector.
This is a quote from the latest product catalog of a a well known producer: "Users of fuse holders designed to comply only with UL/CSA requirements are accustomed to a fuse carrier with a knurled cap that makes it easy to access and change a fuse without tools. Various international equipment standards, however, limit the degree of user accessibility to a fuse holder in order to minimize the possibility of electrical shock to a non-technical user. The limited access fuse holder is designed to require the use of a tool (usually a screwdriver). It also incorporates additional insulation and insulating barriers that eliminate the presence of live conducting services during fuse change operations."
I attack a picture of the fuse carrier style I usually see on modern equipments, I use this type of fuse holder or the one that is integrated in the IEC mains connector.
Attachments
Thanks for the dip.
The electrical rules here are not linked to USA (since Brazil is a Comunist country economically closed, tax rates usually are 100% on any product) or Euro zone, instead they made his own hybrid electrical standards as TV colour PAL-M, 3 pins home mains outlets, 127V/220V/360V mains in homes etc
The electrical rules here are not linked to USA (since Brazil is a Comunist country economically closed, tax rates usually are 100% on any product) or Euro zone, instead they made his own hybrid electrical standards as TV colour PAL-M, 3 pins home mains outlets, 127V/220V/360V mains in homes etc
Where in the amp is the fuse being used?
By far the most common fuse type used in amps for mains side and secondary side protection is the 5x20 (M205) style - so there is that advantage.
For mains side, I'd recommend integrating the socket and switch and fuse if at all possible, as that minimises incorrect wiring and the fuse requires the plug to be removed first before fuse access is available. The only hassle with that type of combo is that it needs the correct cable lugs and a crimper to be used.
By far the most common fuse type used in amps for mains side and secondary side protection is the 5x20 (M205) style - so there is that advantage.
For mains side, I'd recommend integrating the socket and switch and fuse if at all possible, as that minimises incorrect wiring and the fuse requires the plug to be removed first before fuse access is available. The only hassle with that type of combo is that it needs the correct cable lugs and a crimper to be used.
Thanks for the tip, usually I avoid US shop as the ship is expensive, PE charge $49.50 for ship to small partsFor safety hardware, buy from Arrow, RS, Mouser etc unless you know the sellers very well.
Where in the amp is the fuse being used?
I dont know, I will let it in the hands of the builder himself, but it will have two power transformer, hi/low V, so two fuses seems correct.
Thanks for the tip above it seems logical, I will pass it to the builder.
Here is an excellent online reference from our own Merlin Blencowe:
The Valve Wizard
I personally like flush panel mount fuses on the primary of the mains transformer. This is because it is tedious to use a screwdriver to remove the cap, making it a bit more idiot proof than the ones that can be unscrewed by fingers alone. If the mains fuse continues to blow, there is no sense in continuously swapping it out, and there is a real risk that there will be more damage done (see example below).
Even in "communist" countries you should be able to source this kind of fuse holder for about a dollar apiece. I like to use fast blow fuses here and they can be the cheap glass kind that are (hopefully) easy to find.
It can be a very good idea to put a secondary fuse on the HT (before the rectifier). This is because if the HT shorts to ground, it might not draw enough current to blow the mains fuse.
Example: If the mains fuse is too easy to replace, and the user (idiot) decides to put in a higher than intended rated one, the mains transformer might become damaged if the cause is an HT short.
So an HT secondary fuse (you might need two - look at the link above) can be a good idea. I like to use old-school lug style fuse holders here. I mount them inside the chassis, easily and safely accessible, not near any earth/ground point, B+ etc. for service purposes. I typically use slow-blow fuses (T-type) which are hopefully not glass. I suspect that these sorts of fuses may be a bit tricky to source in "communist" countries.
You need to be careful with the HT socket, as they often look similar but are not all equal. Littlefuse has sockets rated to 600V and specify in their documentation that the dielectric strength is 1500V minimum. The dielectric is glass reinforced thermoplastic. These are fine for most of my projects, and mouser sells them for about a dollar apiece.
You might find a different solution for HT secondary fuses than what I do.
Ian
The Valve Wizard
I personally like flush panel mount fuses on the primary of the mains transformer. This is because it is tedious to use a screwdriver to remove the cap, making it a bit more idiot proof than the ones that can be unscrewed by fingers alone. If the mains fuse continues to blow, there is no sense in continuously swapping it out, and there is a real risk that there will be more damage done (see example below).
Even in "communist" countries you should be able to source this kind of fuse holder for about a dollar apiece. I like to use fast blow fuses here and they can be the cheap glass kind that are (hopefully) easy to find.
It can be a very good idea to put a secondary fuse on the HT (before the rectifier). This is because if the HT shorts to ground, it might not draw enough current to blow the mains fuse.
Example: If the mains fuse is too easy to replace, and the user (idiot) decides to put in a higher than intended rated one, the mains transformer might become damaged if the cause is an HT short.
So an HT secondary fuse (you might need two - look at the link above) can be a good idea. I like to use old-school lug style fuse holders here. I mount them inside the chassis, easily and safely accessible, not near any earth/ground point, B+ etc. for service purposes. I typically use slow-blow fuses (T-type) which are hopefully not glass. I suspect that these sorts of fuses may be a bit tricky to source in "communist" countries.
You need to be careful with the HT socket, as they often look similar but are not all equal. Littlefuse has sockets rated to 600V and specify in their documentation that the dielectric strength is 1500V minimum. The dielectric is glass reinforced thermoplastic. These are fine for most of my projects, and mouser sells them for about a dollar apiece.
You might find a different solution for HT secondary fuses than what I do.
Ian
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From countless years I use these
4pcs Sci R3-12 Panel Mount Chassis Fuse Holder for 5x20mm Glass Fuses 10a 250v | eBay
Note that they are "idiot proof" it says clearly "FUSE"
4pcs Sci R3-12 Panel Mount Chassis Fuse Holder for 5x20mm Glass Fuses 10a 250v | eBay
Note that they are "idiot proof" it says clearly "FUSE"
Unless you poke your finger in and touch the threaded section when it is connected to active and the mains is switched onNote that they are "idiot proof" it says clearly "FUSE"
Unless you poke your finger in and touch the threaded section when it is connected to active and the mains is switched on
With that same criteria I could put a nail in the mains plug, and I don't do that from I was five.
Putting a screwdriver (10KV max) on a HT valve rectifier (25KV) does not count because I had twelve at that time, but believe me, it hurts.
In this scenario bayonet fuses are not suited to critical appliances as military or medical, it was good you mention it.Unless you poke your finger in and touch the threaded section when it is connected to active and the mains is switched on
There is another danger here... Inserting a fuse, even held in the cap, when there is a high voltage present on the threaded collar.Unless you poke your finger in and touch the threaded section when it is connected to active and the mains is switched on
It's too easy for a non-technical user to attempt to change a blown fuse without removing AC power, thinking the unit must be safe because the fuse has blown. The threaded collar could contact the incoming new fuse, and the user holding that fuse or the threaded cap holding that fuse then gets a nasty shock. Even fuse holders with a plastic thread and using a metal ring to make the connection to the removable cap have this risk unless they are suitably designed.
Hi boys,
I just had found two nice Fuse Holders, they are both screw type, 5 x 20mm, 10A 250V, they just differs on the top cap shape and one is longer(R3-260).
One is R3-12 other R3-26, price is similar, I will appreciated your comments:
4PC SCI R3-12 Panel Mount Chassis Fuse Holder For 5x20mm Glass Fuses 10A 250V B1 | eBay
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4PC SCI R3-26 Panel Mount Chassis Fuse Holder For 5x20mm Glass Fuses 10A 250V B1 | eBay
I just had found two nice Fuse Holders, they are both screw type, 5 x 20mm, 10A 250V, they just differs on the top cap shape and one is longer(R3-260).
One is R3-12 other R3-26, price is similar, I will appreciated your comments:
4PC SCI R3-12 Panel Mount Chassis Fuse Holder For 5x20mm Glass Fuses 10A 250V B1 | eBay
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+++
4PC SCI R3-26 Panel Mount Chassis Fuse Holder For 5x20mm Glass Fuses 10A 250V B1 | eBay
I've used that top style a bunch of times, I like them. I wire them so that the "hot" side is the innermost contact, so even if it were powered there is little risk if someone were to unscrew the cap while live, at least with a blown fuse...
On some really strange or unusual builds I've put the entire fuseholder inside, so you have to open up the amplifier to change them, forcing you to at least look inside and do a little due diligence as to safety and troubleshooting. Even better, if designing ones own PCB, you could set it up so that it uses PCB mounted push-in contacts for accepting the fuse.
On my personal equipment, I know better than to attempt to change fuses while the equipment is powered!
On some really strange or unusual builds I've put the entire fuseholder inside, so you have to open up the amplifier to change them, forcing you to at least look inside and do a little due diligence as to safety and troubleshooting. Even better, if designing ones own PCB, you could set it up so that it uses PCB mounted push-in contacts for accepting the fuse.
On my personal equipment, I know better than to attempt to change fuses while the equipment is powered!
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