Fake fuses? - Page 1
Forum section: electronics / projects

author: Unknown
author_rank: Unknown
timestamp: December 22, 2015, 05:44:26 pm
content: http://www.ebay.com/itm/311340712562?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITI blew the 500ma fuse in my multi-meter the other day, and thought I'd replace it...So I ordered a set of 5 0.5a fuses shown above.Quality wise they look ok.They are rated for 500 mA 250v, I've been putting 1 amp through one of them for 30 minutes, no problem at all.2 amps, and it burned out after 60 seconds.Does that seem right to you guys for a .500 mA fast acting fuse ?

author: Unknown
author_rank: Unknown
timestamp: December 22, 2015, 05:49:42 pm
content: Quote from: Fungus on December 22, 2015, 05:46:41 pmI hooked it up to my Korad psu via the 10a line on my multimeter, set the psu to 500mA @ 31v first. no problem, upped it to 1a for 30 minutes no problems, at 2a it burned out after 60 seconds.It topped out at 0.42v btw.

author: Fungus
author_rank: Super Contributor
timestamp: December 22, 2015, 05:54:08 pm
content: Obviously they can't make it blow instantly at 501mA but I would expect a tolerance of 50% at most, and it would blow quite fast at that load.60 seconds at 400% load is waaaay too long.

author: Unknown
author_rank: Unknown
timestamp: December 22, 2015, 05:54:48 pm
content: I'll ask for a refund

author: Fungus
author_rank: Super Contributor
timestamp: December 22, 2015, 05:54:59 pm
content: Quote from: SantaClaw on December 22, 2015, 05:49:42 pmVoltage doesn't really matter. Fuses aren't supposed to drop much voltage.

author: Unknown
author_rank: Unknown
timestamp: December 22, 2015, 05:55:51 pm
content: Quote from: Fungus on December 22, 2015, 05:54:59 pmYeah, it was a dead short after all.

author: bookaboo
author_rank: Frequent Contributor
timestamp: December 22, 2015, 05:56:08 pm
content: Sounds normal enough, nominal fuse ratings can be misleading.Always best to check the datasheet.....http://docs-europe.electrocomponents.com/webdocs/135f/0900766b8135f350.pdfFrom this information 210% current can take up to 30 minutes to blow the fuse.Fuses are one part I'd never skimp on or get from ebay. Whatever the cost I'd stick to reputable distributors.Did a quick test of the 500mA version of this particular part on my bench, lasted 14 minutes at 1A (~18°C ambient)

author: SeanB
author_rank: Super Contributor
timestamp: December 22, 2015, 05:57:26 pm
content: Fake car fuses are very common, so much so that quite a few major retailers have had to issue recalls on them, as they all were the same stamping of around 30A rating but were marked and placed in lower current packs.Those were probably made on the cheap using the night shift, using whatever caps and wire was in the assorted machines. So if they had been turning out 1.5A fuses that afternoon and the fuse wire was still in there, and they had the end of a box of 500mA fuses then yours was the result. At least you got fuse wire in there, there have been some with 20A wire inside.

author: Unknown
author_rank: Unknown
timestamp: December 22, 2015, 05:58:48 pm
content: Hm.. according to that chart, it should blow in less than 2 seconds at a 275% load.That's 275% out of 500mA = 1.375A lol ! + 500mA of course, so 275% would be 1.875AI'll check

author: Fungus
author_rank: Super Contributor
timestamp: December 22, 2015, 06:01:28 pm
content: Quote from: bookaboo on December 22, 2015, 05:56:08 pmThat's for glass fuses. Ceramics are filled with sand, sand can conduct a bit of heat away.Was it even getting warm at 1A?

author: Unknown
author_rank: Unknown
timestamp: December 22, 2015, 06:03:17 pm
content: I put a thermocouple on it, it was 3c over room temp, though, now that I'm running it at 1.370a it's 23c in the room, and the surface of it is about 28c Edit: 34c and climbing it seemsNope, It doesn't go above 34c it seems.

author: retrolefty
author_rank: Super Contributor
timestamp: December 22, 2015, 06:04:45 pm
content: Quote from: Fungus on December 22, 2015, 05:54:59 pmWell the are when they blow open.

author: Fungus
author_rank: Super Contributor
timestamp: December 22, 2015, 06:07:14 pm
content: Quote from: SantaClaw on December 22, 2015, 06:03:17 pmSomething is definitely wrong. Those fuses aren't rated properly.You've got a few of them. What current does it take to blow one in less 5 seconds? (for example)

author: calzap
author_rank: Frequent Contributor
timestamp: December 22, 2015, 06:17:52 pm
content: One more thing never to buy from China. Don't think there is a non-destructive way to test cartridge fuses. I think there are CSA, DVE, SEMKO and a few other certifying logos on the things too. Was probably a matter of how many the manufacturer knew of and could fit on the ends.Mike in California

author: Unknown
author_rank: Unknown
timestamp: December 22, 2015, 06:23:21 pm
content: Still going at 2.5A after 1.5 minutes !! lol 500% above rated capacity.Dang, that one was Hot... lol doing 1.2v at the end, so 3w..Will try one at 3A 600% overloadBlew instantly.2.5A = 4 seconds. I don't think they are all the same.. lol

author: SharpEars
author_rank: Unknown
timestamp: December 22, 2015, 06:31:04 pm
content: Quote from: SantaClaw on December 22, 2015, 06:23:21 pmYeah ceramics from China - not a good idea. I would definitely buy the glass ones to be able to see if the filament wire at least looked consistent from fuse to fuse...

author: Unknown
author_rank: Unknown
timestamp: December 22, 2015, 06:34:22 pm
content: Quote from: SharpEars on December 22, 2015, 06:31:04 pmBetter still, I'll go to a local retailer tomorrow.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: December 22, 2015, 06:36:48 pm
content: Quote from: SantaClaw on December 22, 2015, 06:23:21 pmHere is a test procedure you can use. Let's say the fuse is good enough if blows at 210% current before 1/2 hour.1. Slowly ramp up the current to 210%. If it is not blown after 1/2 hour, then the fuse is not good.2. If the fuse blows, then it was one you could have used.It worked for witches!

author: SharpEars
author_rank: Unknown
timestamp: December 22, 2015, 06:38:20 pm
content: Quote from: Tomorokoshi on December 22, 2015, 06:36:48 pmIn other news, Radio Shack in the states sells UL Listed fuses for "dirt cheap." About $2.50 for a package of four or thereabouts.

author: Fungus
author_rank: Super Contributor
timestamp: December 22, 2015, 07:40:34 pm
content: Quote from: SantaClaw on December 22, 2015, 06:23:21 pmI'd rate them at about 1500mA based on that info.

author: SharpEars
author_rank: Unknown
timestamp: December 22, 2015, 09:48:10 pm
content: Quote from: Fungus on December 22, 2015, 07:40:34 pm

author: Unknown
author_rank: Unknown
timestamp: December 22, 2015, 11:01:29 pm
content: Well, it's for my multi meter, I suppose I want them to blow fast?

author: Unknown
author_rank: Unknown
timestamp: December 30, 2015, 12:08:46 pm
content: So the seller replied :

author: Unknown
author_rank: Unknown
timestamp: December 30, 2015, 12:24:30 pm
content: YupThough they haven't removed the item from ebay... lol

author: SharpEars
author_rank: Unknown
timestamp: December 30, 2015, 03:13:22 pm
content: Quote from: SantaClaw on December 30, 2015, 12:08:46 pmAnd then you go back to eBay and see that their same listing is still up and they are selling the same damn things for the same damn price.In other words, lies, all lies. And, by the way, if this was the wrong part, why is the fuse marked 0.5 amps? Huh?You'll get your money back and the seller will continue peddling his crippled wares to other unsuspecting customers.