# Electronics fuse question **URL:** \ **Category:** Factual Questions\ **Created:** [September 13, 2020, 3:26pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492 "2020-09-13T15:26:11Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![a6ka97](https://avatars.discourse-cdn.com/v4/letter/a/c2a13f/32.png) [@a6ka97](https://boards.straightdope.com/u/a6ka97)\ **Post date:** [September 13, 2020, 3:26pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/1 "2020-09-13T15:26:11Z")
I have a blown fuse on a controller for a piece of equipment I have. The fuse is mounted inside the control box by the circuit board. It has what I always called a Buss fuse (although that is probably the brand name) which is a glass tube with metal ends and a wire passing through. The reason the fuse blew, I think, was a thunderstorm went through last week and the lights flashed and the power was out for a few minutes. The fuse is labeled “F6.3A250V” The parts manual list the “ACME” part number and mentions “Use only genuine “ACME” parts” and “Failure to use genuine “ACME” parts will void warranty”. Looked up the part number and they want $15.00 + $5.00 shipping for 1 fuse. Not worried about a warranty as the it is 15+ years old. On eBay I can get 20 (or more) F6.3A250V fuses for the same price they want for 1. Would there be a reason why a fuse off of eBay would be any different that the “genuine ACME” fuse from the manufacturer? ---
**Author:** ![MindsEye\_Watering](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mindseye_watering/32/3619_2.png) [@MindsEye\_Watering](https://boards.straightdope.com/u/MindsEye_Watering)\ **Post date:** [September 13, 2020, 3:40pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/2 "2020-09-13T15:40:37Z")
Is the warranty still valid? If not, use the cheaper fuses. ---
**Author:** ![DavidNRockies](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidnrockies/32/6279_2.png) [@DavidNRockies](https://boards.straightdope.com/u/DavidNRockies)\ **Post date:** [September 13, 2020, 3:54pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/3 "2020-09-13T15:54:01Z")
My thoughts: How expensive/important is the electronic device that uses this fuse ? How long did _this_ fuse last ? Do you have any reason to believe there’s a problem (that caused the fuse to blow) ? How much does the $20 mean to you ? The possible difference between the OEM part and the eBay version is quality assurance. If the eBay version is a piece of shit, then the three amp fuse may not blow at twice that many amps, possibly causing significant damage to other components. Do you have the ability to put a known number of amps through a couple of those 20 low-price fuses … to be sure they actually do blow at three amps ? If you did … and they _did_ blow at 3A … then I’d trust them. If the $20 doesn’t mean a lot, and/or the device does, and/or you really don’t _need_ 20 fuses … I’d buy the OEM version. And you shouldn’t really _need_ 20 of these fuses for one fused circuit on one device. Not for any reason that I can think of, anyway. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [September 13, 2020, 4:08pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/4 "2020-09-13T16:08:27Z")
You should be O.K. to use a fuse rated for 6.3 A and 250 V _as long as it was made_ by a reputable manufacturer such as Littelfuse or Bussmann. Is it a standard, fast blow, or slow blow fuse? Because you’ll also want to match that, too. Keep in mind that there’s a lot of counterfeit parts out there. I would **not** buy it from Amazon or eBay, as they’re flooded with imitation and counterfeit stuff. I recommend buying it from Mouser or Digi-Key. ---
**Author:** ![DavidNRockies](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidnrockies/32/6279_2.png) [@DavidNRockies](https://boards.straightdope.com/u/DavidNRockies)\ **Post date:** [September 13, 2020, 4:12pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/5 "2020-09-13T16:12:32Z")
I misread the part number (need coffee). @Crafter_man read it right. 6.3A, _not_ 3A. Mea culpa. ---
**Author:** ![a6ka97](https://avatars.discourse-cdn.com/v4/letter/a/c2a13f/32.png) [@a6ka97](https://boards.straightdope.com/u/a6ka97)\ **Post date:** [September 13, 2020, 4:13pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/6 "2020-09-13T16:13:12Z")
I haven’t used the machine for a week or so, went to use it and no power. Found the blown fuse so I would be more concerned if it blew while it was running, but it wasn’t, and that led me to the thunderstorm and the power going on/off for the reason for the blown fuse. I have had it for several years and this is the 1st time it has blown. I don’t need 20 of the fuses, but if I can get the same thing for $2.00, if available locally, and not $20.00 for the “genuine” I would probably want to save the money. A thunderstorm blowing the fuse might explain why the previous owner had an in-line on/off switch in addition to the on/off switch on the control box. Turn the in-line switch off and don’t need to worry about thunderstorms or power outages blowing the fuse, especially at $20.00 a pop. Not that I am buying off of eBay, just doing a search of what is available. ---
**Author:** ![DavidNRockies](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidnrockies/32/6279_2.png) [@DavidNRockies](https://boards.straightdope.com/u/DavidNRockies)\ **Post date:** [September 13, 2020, 4:14pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/7 "2020-09-13T16:14:57Z")
> [@Crafter\_Man](#): > > Is it a standard, fast blow, or slow blow fuse? Because you’ll also want to match that, too. The “F” in his part number [should stand for fast](https://www.swe-check.com.au/pages/learn_fuse_speed.php). ---
**Author:** ![a6ka97](https://avatars.discourse-cdn.com/v4/letter/a/c2a13f/32.png) [@a6ka97](https://boards.straightdope.com/u/a6ka97)\ **Post date:** [September 13, 2020, 4:16pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/8 "2020-09-13T16:16:06Z")
Thanks for that bit of information. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [September 13, 2020, 4:31pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/9 "2020-09-13T16:31:46Z")
> [@DavidNRockies](#): > > The “F” in his part number [should stand for fast](https://www.swe-check.com.au/pages/learn_fuse_speed.php). Ahh, good catch. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [September 13, 2020, 4:39pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/10 "2020-09-13T16:39:35Z")
It’s been many years since I had to buy any of those, but the classic glass-tube fuses were often sold at auto parts stores. They’d have a whole rack of little cases with 5 fuses in a case. Back in the day they were $1 for a 5-pack. Nowadays probably $5 for the same 5-pack. Rather than fiddling with online, shipping delays, questionable merchandise, etc., if you have a good car parts store nearby it might be worth calling or stopping by. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [September 13, 2020, 4:47pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/11 "2020-09-13T16:47:53Z")
I would echo **Crafter\_Man** and avoid Amazon and eBay where electrical specs matter - they are both rife with counterfeit parts that look correct. Like he suggests, I’d stick with reputable distributors like Mouser or Digi-Key. They’re not that much more expensive, minus shipping costs: [https://www.digikey.com/short/z239f0](https://www.digikey.com/short/z239f0) ---
**Author:** ![DavidNRockies](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidnrockies/32/6279_2.png) [@DavidNRockies](https://boards.straightdope.com/u/DavidNRockies)\ **Post date:** [September 13, 2020, 4:50pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/12 "2020-09-13T16:50:11Z")
> [@Crafter\_Man](#): > > I recommend buying it from Mouser or Digi-Key. +1 A fast look at [Digi-Key](https://www.digikey.com/) shows they carry a couple of inexpensive options. Just watch that the dimensions (length and diameter) of the one you’re looking at are an exact match for the one you’re replacing. DAMHIKT ---
**Author:** ![3AxisCtrl](https://avatars.discourse-cdn.com/v4/letter/3/ecd19e/32.png) [@3AxisCtrl](https://boards.straightdope.com/u/3AxisCtrl)\ **Post date:** [September 13, 2020, 9:11pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/13 "2020-09-13T21:11:32Z")
I doubt there’s much risk associated with using the cheapest replacement fuse you can find. The original lasted 15 years, and it apparently took an electrical storm to damage it. On this evidence, soldering a piece of wire in place of the fuse\* seems likely to give years more service. \*Yes, a very unsound practice. ---
**Author:** ![a6ka97](https://avatars.discourse-cdn.com/v4/letter/a/c2a13f/32.png) [@a6ka97](https://boards.straightdope.com/u/a6ka97)\ **Post date:** [September 13, 2020, 9:41pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/14 "2020-09-13T21:41:19Z")
Checked some auto parts stores. The fuse is a 5mm X 20mm and the automotive fuses in stock are bigger around. Looked at the Digi-Key website and will order some Littelfuse branded fuses from them. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 13, 2020, 9:43pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/15 "2020-09-13T21:43:28Z")
Just stick a penny in it 😉 ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [September 13, 2020, 10:02pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/16 "2020-09-13T22:02:30Z")
> [@3AxisCtrl](#): > > I doubt there’s much risk associated with using the cheapest replacement fuse you can find. The tolerance on cheap fuses is horrible. If you have a cheap 6 amp fuse, it is guaranteed NOT to blow at anything under 6 amps. At some point above 6 amps it will blow. Might be 6.1 amps, might be 7 amps, heck it might even be 9 amps or higher for a real cheapie piece of crap fuse. The tighter the tolerance, the closer to 6 amps it will blow, and also (generally) the more expensive the fuse will be. The OP’s fuse is 6.3 amps, which indicates a higher tolerance than just a 6 amp fuse. You would have to look up the data sheet for the original fuse to see what it’s actual tolerance is. As for the OP, I hope you are right that it’s only a fuse that blew. One thing that can happen with lightning is that the lightning bolt raises the ground potential above the device’s power supply voltage, which can cause semiconductors to “latch up”. Basically, this creates a temporary short circuit through the semiconductor, which could have caused the fuse to blow. If the fuse didn’t blow fast enough, the overcurrent from the latchup could cause permanent damage to the semiconductor, so be prepared for the possibility that it’s not just a blown fuse. FYI, Buss is indeed a brand name. The technical name of that type of fuse is glass cartridge fuse. A lot of people call them Buss fuses. ---
**Author:** ![MindsEye\_Watering](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mindseye_watering/32/3619_2.png) [@MindsEye\_Watering](https://boards.straightdope.com/u/MindsEye_Watering)\ **Post date:** [September 13, 2020, 11:38pm UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/17 "2020-09-13T23:38:12Z")
> [@TriPolar](#): > > Just stick a penny in it 😉 That’s a 50 amp “no-blo” fuse. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 14, 2020, 1:20am UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/18 "2020-09-14T01:20:43Z")
You don’t happen to be Wile E. Coyote, do you? ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [September 14, 2020, 3:09am UTC](https://boards.straightdope.com/t/electronics-fuse-question/920492/19 "2020-09-14T03:09:24Z")
There is a lot of hidden engineering in fuses. Shoddy fake fuses are not a good risk as they can violate any number of the safety engineering aspects of design and construction that are not at all obvious. But you can be sure that the replacement part price for the fuse is just usual massive markup inherent in any spare part and they will actually be shipping exactly the same part as you would find from a reputable source. They just charge you any eye watering markup to cover their costs of managing a spare parts inventory.