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Electronics => Repair => Topic started by: Chris Wilson on October 18, 2012, 07:07:48 pm

Title: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: Chris Wilson on October 18, 2012, 07:07:48 pm
I have an odd ball size panel fuse holder with a ceramic cartridge type fuse in it that's blown. I can't easily seem to find a supplier over here in the UK for a replacement. Can I drill out the end caps where the original fuse wire was soldered in manufacture and make up another 25 Amp fuse using a strand of 20 Amp fuse wire twisted together with a strand of 5 Amp fuse wire in parallel and solder this in?

TI don't see why not but I may be missing something. It's a fuse for a 25 Amp Variac on UK 230 volts mains. Thanks.
Title: Re: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: SeanB on October 18, 2012, 07:22:51 pm
Picture of the oddball fuse?
Title: Re: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: Chris Wilson on October 18, 2012, 09:00:34 pm
Here are some shots of fuse and panel holder. Probably from 50's UK military gear, knowing the source. Holder is UK made Belling Lee. Thanks Sean!
Title: Re: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: ptricks on October 18, 2012, 09:00:45 pm
The short answer is no, it would be dangerous to do that.
The long answer is you can use a wire in place of the original fuse IF you test the wire you will be using at the rated current to see if it does indeed blow at the current you need. You cannot just take a wire that is the correct size and assume that it will have the same current capability of the fuse wire because you do not know what alloy is used in the fuse or the alloy of the wire you would like to use.  Very few copper wire are 100% copper, pure copper is hard and doesn't bend well without cracking , so most wire has other metals blended with the copper to make it less prone to breakage when bending. You also would need to test the exact same length of wire that would be used in the fuse , longer wire would have higher current capability because of the increased surface area.  Joining 2 different wires is a definite no.



Title: Re: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: Chris Wilson on October 18, 2012, 09:05:29 pm
The short answer is no, it would be dangerous to do that.
The long answer is you can use a wire in place of the original fuse IF you test the wire you will be using at the rated current to see if it does indeed blow at the current you need. You cannot just take a wire that is the correct size and assume that it will have the same current capability of the fuse wire because you do not know what alloy is used in the fuse or the alloy of the wire you would like to use.  Very few copper wire are 100% copper, pure copper is hard and doesn't bend well without cracking , so most wire has other metals blended with the copper to make it less prone to breakage when bending. You also would need to test the exact same length of wire that would be used in the fuse , longer wire would have higher current capability because of the increased surface area.  Joining 2 different wires is a definite no.


My post wasn't worded at all well, sorry. I have modified it. The wire I wanted to use in the fuse is old fashioned FUSE wire of known rating. The type you would have used in domestic consumer 's unit before the new fangled RCD's and MCB's came along. I see my original post looked like I was goiung to use 25 amp rated insulated cable with the insulation stripped off :)
Title: Re: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: SeanB on October 19, 2012, 04:37:26 am
How about just using a 25A 6.3 by 32 fuse in it? A little thinner but will still fit the holder. Use the HRC version and it will work.
Title: Re: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: Chris Wilson on October 19, 2012, 07:24:21 pm
How about just using a 25A 6.3 by 32 fuse in it? A little thinner but will still fit the holder. Use the HRC version and it will work.

Hmm, that's a good idea, I have just tried one, wrong amperage, but physically 6.3 x 32 mm. Does the fact it only contacts on the ends of the end caps matter at 25 Amps? The correct size fuse is a good tight fit in a sprung collar down the SIDES of the caps, as well as under pressure on the ENDS of the caps, if you follow?  You don't fancy my idea of using commercial fuse wire to uprate the fuse cartridge that came with it, but of wrong Amperage, by removing original wire and fitting a new strand made of 20 and 25 Amp wire twisted together? Cheers Sean!
Title: Re: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: SeanB on October 19, 2012, 07:32:50 pm
The fuse wire will work, but most is not really solderable. you might find you will have to just flip it over the end but not past the end of the cap.

Can you not just replace the holder with a modern one, that will fit the hole ( with or without having to make a spacer washer to fill any gap) and which takes a modern cheap 6.3x32 fuse?
Title: Re: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: Chris Wilson on October 19, 2012, 07:53:26 pm
That's what I was trying to avoid Sean, it's a bloody big `ole and modern ones are smaller. I have a half decent home machine shop so could turn a flanged spacer washer, but I am getting lazy in my old age. I guess some of these old fuse cartridges are now obsolete. I'll have a look around and see what options are easily available to update the whole caboodle. Cheers, appreciate your time!
Title: Re: Odd ball cartridge fuse blown, use "fuse wire" to repair?
Post by: SeanB on October 20, 2012, 06:02:05 am
Pretty sure you can get a modern one that will fit in the hole.