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Fuse rating question

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Posted on July 12, 2021 at 12:51:14
tweaker456
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Posts: 3092
Location: SF Bay Area
Joined: June 20, 2020
If the designer of a low current devise like a pre-amp calculates for a fuse of 200ma would it then be ok, safe, kosher to ignore that number and put in a 500ma fuse which is 2.5 times the current rating the one the designer of the amp thought appropriate? Thanks, Tweaker456


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RE: Fuse rating question, posted on July 13, 2021 at 21:21:17
John Elison
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No, you shouldn't exceed the current rating recommended by the manufacturer. Otherwise, you run the risk of doing serious damage to the component if a fault occurs in the component and the fuse doesn't blow at 200-ma to provide the required protection.

Good luck,
John Elison

 

RE: Fuse rating question, posted on July 13, 2021 at 22:41:54
pictureguy
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Posts: 15369
Location: SoCal
Joined: October 19, 2008
fuses are NOT brick walls. A 1 amp fuse doens't pop at 1.01 amps instandtly.
You'll have to look at the time / current charts on the LITTLEFUSE website.

Also? As near as I can figure, you have 3 types of fuse.
Standard.....in MOST equipement regardles of current
Slo-Blow....Maybe the next most common, and will withstand higher current / time before fusing
And
FAST blo, used in some delicate electronics. Thsese pop as nearly instantly as they can engineer.

NEVER over curren the fuse. A POSSIBLE but not recommended exception? Gear requries a 2 amp slo-blo. I dont' know, but you MAY get away with a slightly larger, standard type-fuse.....But I have never heard of anyone actually DOING SO......You may want to write to an applications guy at one of the big fuse companies.
Too much is never enough

 

RE: Fuse rating question, posted on July 14, 2021 at 10:05:05
tweaker456
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Posts: 3092
Location: SF Bay Area
Joined: June 20, 2020
Hum, that funny. Over at Tweaker's Asylum duster is recommending a 500ma fuse in a pre-amp that came with a 200ma fuse.


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RE: Fuse rating question, posted on July 14, 2021 at 10:41:17
Davey
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Posts: 2254
Joined: September 26, 2013
Well, if you have a legitimate failure you'd probably pop either fuse.

Sizing fuses on equipment can be more tricky than it might seem. You want to provide protection, but you also don't want nuisance openings during turn-on either. It's an iterative process, somewhat.

Cross-posting into another area so you could needle Duster is funny.

Dave.

 

RE: Fuse rating question, posted on July 14, 2021 at 10:43:03
tweaker456
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Posts: 3092
Location: SF Bay Area
Joined: June 20, 2020
Probably maybe but not definitely.


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Good point!, posted on July 14, 2021 at 12:44:12
John Elison
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Posts: 23215
Location: Central Kentucky
Joined: December 20, 2000
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Since you're the owner, you can actually use any size fuse you want that's equal to or greater than 200-mA. So long as no circuit faults occur, you'll be just fine. But, if anything should happen to go wrong, there's greater risk of serious damage when using a fuse larger than 200-mA.

Best regards,
John Elison

 

RE: Fuse rating question, posted on July 14, 2021 at 14:07:14
tweaker456
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Posts: 3092
Location: SF Bay Area
Joined: June 20, 2020
If I recommended a fuse 2.5 times what the designer calculated for I would have been nail to a cross. I can tell you that!




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RE: Fuse rating question, posted on July 14, 2021 at 14:46:37
Davey
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Posts: 2254
Joined: September 26, 2013
No, but you probably would have been questioned about it. :)
I'm not sure why you're twisted up about this. I quit taking Duster seriously years ago.

Dave.

 

RE: Fuse rating question, posted on July 14, 2021 at 17:32:04
tweaker456
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Posts: 3092
Location: SF Bay Area
Joined: June 20, 2020
+1


Denied facts are still facts.

 

RE: Fuse rating question, posted on July 15, 2021 at 07:25:40
sony6060
Audiophile

Posts: 962
Location: SE MI
Joined: August 8, 2014
Fast Blow fuse, use 2x current draw. Slow Blow fuse, use 1.25 times the current draw. Fuses can operate up to 1.5x the fuse current rating for up to 20 minutes.
Personally, I use Slow blow at as close to current draw as possible with capacitor input power supplies. Choke input power supplies not having a high input charging surge, I use Fast Blow at as close to current rating as possible. Never had a fuse fail.

 

Try this view, posted on July 20, 2021 at 08:47:56
mlsstl
Audiophile

Posts: 626
Location: Midwest
Joined: September 1, 2015
Most circuits have multiple components. Consider that, with a 200 mA fuse, for example, you may lose one component before the fuse pops, but still protect other components in the circuit. With a 500 mA fuse, you may still be protected from starting a fire, but end up losing multiple components in the circuit before it pops.

 

Since they're cheap, posted on July 27, 2021 at 14:33:49
E-Stat
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April 5, 2002
just get a small supply of the correct value.

 

RE: Fuse rating question, posted on August 30, 2021 at 13:46:17
pictureguy
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Posts: 15369
Location: SoCal
Joined: October 19, 2008
If circuit stayed perfect forever, you would NOT need a fuse.

I'd personally try to get the fuse recommended by the designer / builder.....but that's just me.


Too much is never enough

 

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