In article <fb037dl99i4c3lsdpu7gkjqans34t9qokr@4ax.com>, oldschool@tubes.com says...> One thing I do not understand. > In a store I found some other fuses that were about the same size as the > SFE. It may have been AGW, but I dont remember for sure. They were 1A > fuses rated at 32 volts. They were made out of glass, with the metal > ends, just like the fuses rated at 250V. > > Why would a fuse like that not work at 250 V, or 100 V or any voltage > above 32 V? I'm sure the glass container and metal ends would not fall > apart. And isn't the element inside just a piece of very thin wire whose > gauge is determined by the amperage? So, why wouldn't that fuse work at > a (reasonable) voltage over 32 V? (Or up to 250 V)? > > I'm sure there is a reason, but I sure can not see why? Everything looks > identical. > > > >The reason for the voltage rating is the arc over voltage. That is if the voltage is high enough when the fuse element melts there will be an arc created in the fuse and the current flow will still not be cut off. At work we had some fuses that were about 8 inches long and over an inch in diameter. They were rated for only one amp, but for 6000 or so volts. Fuses that have a higher voltage rating are fine to use in the low voltage applications. They only work on the curent. In those inexpensive meters with fuses only rated for 250 volts, they could be dangerous at higher voltages. We were shown a trainging film by the Fluke salesmen. They showed what could hapen if you had a low voltage fuse and had the meter set for ohms or amps and put it across a 480 volt line with plenty of curent. The fuse would arc over and the leads would melt down. You would too if you were holding the leads. They make some special fuses for them to get the higher CAT ratings.
Need fuses for Multimeter
Started by ●January 30, 2018
Reply by ●January 31, 20182018-01-31
Reply by ●January 31, 20182018-01-31
On Wed, 31 Jan 2018 10:06:34 -0500, Ralph Mowery <rmowery28146@earthlink.net> wrote:>In article <fb037dl99i4c3lsdpu7gkjqans34t9qokr@4ax.com>, >oldschool@tubes.com says... >> One thing I do not understand. >> In a store I found some other fuses that were about the same size as the >> SFE. It may have been AGW, but I dont remember for sure. They were 1A >> fuses rated at 32 volts. They were made out of glass, with the metal >> ends, just like the fuses rated at 250V. >> >> Why would a fuse like that not work at 250 V, or 100 V or any voltage >> above 32 V? I'm sure the glass container and metal ends would not fall >> apart. And isn't the element inside just a piece of very thin wire whose >> gauge is determined by the amperage? So, why wouldn't that fuse work at >> a (reasonable) voltage over 32 V? (Or up to 250 V)? >> >> I'm sure there is a reason, but I sure can not see why? Everything looks >> identical. >> >> >> >> > >The reason for the voltage rating is the arc over voltage. That is if >the voltage is high enough when the fuse element melts there will be an >arc created in the fuse and the current flow will still not be cut off. > >At work we had some fuses that were about 8 inches long and over an inch >in diameter. They were rated for only one amp, but for 6000 or so >volts. > >Fuses that have a higher voltage rating are fine to use in the low >voltage applications. They only work on the curent. In those >inexpensive meters with fuses only rated for 250 volts, they could be >dangerous at higher voltages. We were shown a trainging film by the >Fluke salesmen. They showed what could hapen if you had a low voltage >fuse and had the meter set for ohms or amps and put it across a 480 volt >line with plenty of curent. The fuse would arc over and the leads would >melt down. You would too if you were holding the leads. They make some >special fuses for them to get the higher CAT ratings. >Ok, that makes sense. Apparently the element inside the fuse must melt for a wider gap on higher voltage rated fuses. Which would occur because of the type of metal used and/or shape of the wire. I have seen fuses with that element looking wavy, so I suppose that has something to do with it. This is all mostly just a guess, but something has to make that gap wider to prevent arc-over. I can see arcing at voltages above 250 V. I have worked on lots of old tube tv sets, and have seen the B+ high voltage jump across tube socket pins and other places. Most of the time the voltages were from 300 volts up to nearing 600 volts. Apparently these meters are not really suited for that higher voltage tube gear, even though both the AC and the DC ranges go to 1000 V. I do find the 32 V limit on some of those fuses sort of an oddball figure though. Any voltage from 32 to 100 V is not going to arc much. Even 120 V AC line voltage really does not arc very much. Most of the arcing I have seen has been over 250 V. The CRT anodes on old CRT tv sets were notorious for arcing, but that was several thousand volts. I have seen (and felt) the arcing from electric livestock fences (that bites, and always makes me use my worst vocabulary). Those fences are generally 2000 to 6000 volts. Anyhow, this has been an interesting thread. I learned more about fuses, which I have used for decades but never given much thought to them, other than selecting one that is the right amperage and fits the holder. It is likely I have used automotive fuses on tube gear that were not rated for the voltage. Now I will be more aware of that. Speaking of arcing. There is a youtube video where a main high tension line on a tower is disconnected, and that forms am arc that keeps growing taller. (Called a Jacobs Ladder). If I recall, the voltage is something like 500,000 volts. The guys open 3 switches on the tower (3 phase), and that arc occurs. Those switches are probably one of more feet of gap, but at that voltage it dont seem to matter. That's an awesome video.....
Reply by ●January 31, 20182018-01-31
On Tue, 30 Jan 2018 18:14:36 -0500, Ralph Mowery <rmowery28146@earthlink.net> wrote:>This fuse is known by the Garner Bender part of GF-0306 and it is rated >at 500mA, 250V fast blow. It is also known as F500mA, 250V. >Amazon carries it: www.amazon.com/Littelfuse-500mA-Fast-Blow- >Fuse/dp/B000PHCTP2 >And Ebay: >www.ebay.com/itm/5x-F500mAL250V-F500mA-250V-F500m-L250V-F500mL250V- >cartridge-GLASS-fuse-5X20mm-/151136253242 >Or do a search on Google for "F500mA 250V fuse". The are easily and >readily available. > >End of copy. > >That fuse is probably a metric size fuse. >Just to mention it, I ordered some fuses on Ebay. 5 X 20 mm. I found they wanted around $6.50 for five 500ma fuses. Then I found a whole kit of 100 of that size fuse, for around $7.25. The kit has ten of the 500ma size and ten more each of other amperages, up to 15A. Needless to say, I bought the whole kit for pennies more. Amazon was pulling their usual shit. They list something for a certain price but require a minimum dollar amount order, and add even more if I am not a "prime" member and then add high shipping in the end. I began with a $7 box of fuses and would have had to pay double that amount in the end. Precisely why I never buy from Amazon..... They can keep their bullshit games, and shove their "prime" service up their a$$. The initial item was cheaper on Ebay, and with free shipping, Thats all I paid, and checking out was much quicker too. I dont know why anyone even bothers with Amazon. They're crooks....
Reply by ●January 31, 20182018-01-31
On Tue, 30 Jan 2018 17:15:42 -0500, "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote:>oldschool@tubes.com wrote: >> >> * Now I know why I miss Radio Shack, they usually had stuff like this. > >Are you kidding? Radio Shack had almost nothing. They never would have >had a fuse like that even before they started focusing on toys and cell >phones. > >Haven't you looked at Digi-Key? > >Until Radio Shack closed their doors, they DID have a decent selection of fuses, switches, and certain other parts. They were lacking with capacitors and semiconductors though. Yea, their prices were a little high, but they were convenient.... Places like Digi-Key, Mouser and others like that all have minimum orders, and high shipping. I dont even bother looking on those places anymore, unless I intend to buy a whole bunch of stuff that I dont really need, just to obtain one part.
Reply by ●January 31, 20182018-01-31
Den onsdag den 31. januar 2018 kl. 21.07.57 UTC+1 skrev olds...@tubes.com:> On Wed, 31 Jan 2018 10:06:34 -0500, Ralph Mowery > <rmowery28146@earthlink.net> wrote: > > >In article <fb037dl99i4c3lsdpu7gkjqans34t9qokr@4ax.com>, > >oldschool@tubes.com says... > >> One thing I do not understand. > >> In a store I found some other fuses that were about the same size as the > >> SFE. It may have been AGW, but I dont remember for sure. They were 1A > >> fuses rated at 32 volts. They were made out of glass, with the metal > >> ends, just like the fuses rated at 250V. > >> > >> Why would a fuse like that not work at 250 V, or 100 V or any voltage > >> above 32 V? I'm sure the glass container and metal ends would not fall > >> apart. And isn't the element inside just a piece of very thin wire whose > >> gauge is determined by the amperage? So, why wouldn't that fuse work at > >> a (reasonable) voltage over 32 V? (Or up to 250 V)? > >> > >> I'm sure there is a reason, but I sure can not see why? Everything looks > >> identical. > >> > >> > >> > >> > > > >The reason for the voltage rating is the arc over voltage. That is if > >the voltage is high enough when the fuse element melts there will be an > >arc created in the fuse and the current flow will still not be cut off. > > > >At work we had some fuses that were about 8 inches long and over an inch > >in diameter. They were rated for only one amp, but for 6000 or so > >volts. > > > >Fuses that have a higher voltage rating are fine to use in the low > >voltage applications. They only work on the curent. In those > >inexpensive meters with fuses only rated for 250 volts, they could be > >dangerous at higher voltages. We were shown a trainging film by the > >Fluke salesmen. They showed what could hapen if you had a low voltage > >fuse and had the meter set for ohms or amps and put it across a 480 volt > >line with plenty of curent. The fuse would arc over and the leads would > >melt down. You would too if you were holding the leads. They make some > >special fuses for them to get the higher CAT ratings. > > > > Ok, that makes sense. Apparently the element inside the fuse must melt > for a wider gap on higher voltage rated fuses. Which would occur because > of the type of metal used and/or shape of the wire. I have seen fuses > with that element looking wavy, so I suppose that has something to do > with it. This is all mostly just a guess, but something has to make that > gap wider to prevent arc-over. > > I can see arcing at voltages above 250 V. I have worked on lots of old > tube tv sets, and have seen the B+ high voltage jump across tube socket > pins and other places. Most of the time the voltages were from 300 volts > up to nearing 600 volts. Apparently these meters are not really suited > for that higher voltage tube gear, even though both the AC and the DC > ranges go to 1000 V. > > I do find the 32 V limit on some of those fuses sort of an oddball > figure though. Any voltage from 32 to 100 V is not going to arc much. > Even 120 V AC line voltage really does not arc very much. Most of the > arcing I have seen has been over 250 V.arc welding is done with around 20V, once you get the arc started the the ionized air is like a short and just keep going until the distance gets to large
Reply by ●January 31, 20182018-01-31
In article <cf947dpqa56d68hdob75er2c1r480tbnet@4ax.com>, <oldschool@tubes.com> wrote:>Places like Digi-Key, Mouser and others like that all have minimum >orders, and high shipping.I think your information is outdated. Mouser: "No minimum order dollar amount on products normally stocked in our warehouse." Digi-Key: "There is no minimum order or handling fee." "Except as otherwise provided on the Site, (1) shipping or freight charges and insurance will be paid by the customer*, * When a check or money order accompanies your order, Digi-Key pays all shipping and insurance (our choice for method of shipping) to all addresses in the U.S. and Canada." So, if you want to order a single pack of fuses from Digi-Key, you can do so very inexpensively - simply MAIL them your order (rather than submitting it on-line) and include a check or money order.
Reply by ●January 31, 20182018-01-31
In article <th847dpmrd03t776hj6brr1nfq3t4nf4ch@4ax.com>, oldschool@tubes.com says...> > > Just to mention it, I ordered some fuses on Ebay. 5 X 20 mm. I found > they wanted around $6.50 for five 500ma fuses. Then I found a whole kit > of 100 of that size fuse, for around $7.25. The kit has ten of the 500ma > size and ten more each of other amperages, up to 15A. Needless to say, I > bought the whole kit for pennies more. > > Amazon was pulling their usual shit. They list something for a certain > price but require a minimum dollar amount order, and add even more if I > am not a "prime" member and then add high shipping in the end. I began > with a $7 box of fuses and would have had to pay double that amount in > the end. Precisely why I never buy from Amazon..... They can keep their > bullshit games, and shove their "prime" service up their a$$. > > The initial item was cheaper on Ebay, and with free shipping, Thats all > I paid, and checking out was much quicker too. I dont know why anyone > even bothers with Amazon. They're crooks.... > > > >A while back I ordered some coffee off Amazon. It shipped from Target. I looked at the Target site and it was less from them, so from then on I go to the Target web site. Would go to Target, but it is about 30 miles one way from here. I live in a small town so not too much around here. Even with some shiping charges, it is less expensive for me to order things. Really came out a while back with Best Buy. Ordered a 60 inch TV tht had free shipping. Two people came out and set it up. They turned it on,but said they could not mess with the cable TV as per company policy. They carried off the packing material and offered to carry off the old TV. All that service was free. The nearest BB is about 30 miles away. While I do order from Amazon, I also check other places for the best price.
Reply by ●January 31, 20182018-01-31
oldschool@tubes.com wrote:> > Until Radio Shack closed their doors, they DID have a decent selection > of fuses, switches, and certain other parts. They were lacking with > capacitors and semiconductors though. Yea, their prices were a little > high, but they were convenient....Since it is for a meter, and because you had trouble finding it, I assumed it was an HRC and not a common fuse. Sorry.
Reply by ●January 31, 20182018-01-31
In article <2i647dla33h4gegvdpqbqn6k5ugu9qeein@4ax.com>, oldschool@tubes.com says...> Fuses that have a higher voltage rating are fine to use in the low > >voltage applications. They only work on the curent. In those > >inexpensive meters with fuses only rated for 250 volts, they could be > >dangerous at higher voltages. We were shown a trainging film by the > >Fluke salesmen. They showed what could hapen if you had a low voltage > >fuse and had the meter set for ohms or amps and put it across a 480 volt > >line with plenty of curent. The fuse would arc over and the leads would > >melt down. You would too if you were holding the leads. They make some > >special fuses for them to get the higher CAT ratings. > > > > Ok, that makes sense. Apparently the element inside the fuse must melt > for a wider gap on higher voltage rated fuses. Which would occur because > of the type of metal used and/or shape of the wire. I have seen fuses > with that element looking wavy, so I suppose that has something to do > with it. This is all mostly just a guess, but something has to make that > gap wider to prevent arc-over. > > I can see arcing at voltages above 250 V. I have worked on lots of old > tube tv sets, and have seen the B+ high voltage jump across tube socket > pins and other places. Most of the time the voltages were from 300 volts > up to nearing 600 volts. Apparently these meters are not really suited > for that higher voltage tube gear, even though both the AC and the DC > ranges go to 1000 V. > > I do find the 32 V limit on some of those fuses sort of an oddball > figure though. Any voltage from 32 to 100 V is not going to arc much. > Even 120 V AC line voltage really does not arc very much. Most of the > arcing I have seen has been over 250 V. The CRT anodes on old CRT tv > sets were notorious for arcing, but that was several thousand volts. I > have seen (and felt) the arcing from electric livestock fences (that > bites, and always makes me use my worst vocabulary). Those fences are > generally 2000 to 6000 volts. > > Anyhow, this has been an interesting thread. I learned more about fuses, > which I have used for decades but never given much thought to them, > other than selecting one that is the right amperage and fits the holder. > It is likely I have used automotive fuses on tube gear that were not > rated for the voltage. Now I will be more aware of that. > > Speaking of arcing. There is a youtube video where a main high tension > line on a tower is disconnected, and that forms am arc that keeps > growing taller. (Called a Jacobs Ladder). If I recall, the voltage is > something like 500,000 volts. The guys open 3 switches on the tower (3 > phase), and that arc occurs. Those switches are probably one of more > feet of gap, but at that voltage it dont seem to matter. That's an > awesome video..... > > >There is a lot more to the fuses than meets the eye.. I don't know about the low voltage fuses, but wild guess for the 32 volts is most of them were used in cars and trucks where 24 volt batteries were the highest and the 32 was some safety factor. The 250 volt is good for common house voltages in the US. My Fluke meter has 2 fuses in it and they are both rated for 1000 volts. One is for 11 amps and I don't recall the lower curent one. That is so it will meet the CAT 3 requirements. If you have not heard of the CAT requirements, you should look it up on the internet. I don't know wht the voltage ratings are for my old Simpson 260, but should look one day. I do have abox of fuses that will fit in my Fluke but they are only rated for 600 volts AC. As I don't work around anything but around the house I would use them if one of the origional ones blow. If I was still working and around the 480 vot 3 phase stuff that had 500 amp or more fuses in it, I would only replace with the origional type. I do have a hand full of the Harbor Freight 'free' voms scattered around the house and cars. Good enough for quick checks. They are really very accurate for the price (usually less than 1 % off the Fluke) as I compaired them with some of the Fluke meters. I do remember drawing arcs of several inches off the old black and white TVs. I think they ran about 10 to 12 thousand volts. You mentioned the Jachobs ladder. I have made them out of old neon sign transformers and some furnace igniter transformers and some rods about 2 feet tall.
Reply by ●January 31, 20182018-01-31
Ralph Mowery wrote:> You mentioned the Jachobs ladder. I have made them out of old neon sign > transformers and some furnace igniter transformers and some rods about 2 > feet tall. >I built one with a furnace igniter transformer back in the seventies. I saw this 100kV job about eight years ago. https://www.youtube.com/watch?v=g96AvBV10xU
