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 Post subject: Fuse for 1975 Silverface Champ?
PostPosted: Tue Feb 12, 2013 4:47 pm 
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Is it ok to use a 1A 250V fuse for a silverface Fender Champ? The amp chasis says 1A 125V, but I bought it and there was a 1A 250V fuse in there so I bought those to replace it when it blew and then realized that it said 125V on the chasis. Any ideas?


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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Tue Feb 12, 2013 4:56 pm 
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Do not over-spec the fuse. It's there for a reason -- to save the amp in the event of some calamity.

Also, use the "slo-blow" type for which the amp was designed.

Arjay

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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Tue Feb 12, 2013 5:11 pm 
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Electronics are spec'd for a reason. ALWAYS use the proper fuse. Arjay nailed it with the slo-blow also.

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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Tue Feb 12, 2013 5:15 pm 
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Quote:
Do not over-spec the fuse. It's there for a reason -- to save the amp in the event of some calamity.

Also, use the "slo-blow" type for which the amp was designed.

Arjay


I've been looking for a 1A 125V Slo Blow fuse and I cant find them anywhere. Any ideas where I could get some? :?:


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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Tue Feb 12, 2013 5:54 pm 
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Ahem...Google is your friend. I spent two minutes and found this...and plenty others.

http://www.mouser.com/Circuit-Protectio ... Mgod-g0A6g

HTH

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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Tue Feb 12, 2013 6:06 pm 
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T2Stratman wrote:
Ahem...Google is your friend. I spent two minutes and found this...and plenty others.

http://www.mouser.com/Circuit-Protectio ... Mgod-g0A6g

HTH

T2


Thanks, I checked it out but they don't have the one I'm looking for. Rare fuse I guess.


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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Tue Feb 12, 2013 6:30 pm 
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Bedlam9 wrote:
T2Stratman wrote:
Ahem...Google is your friend. I spent two minutes and found this...and plenty others.

http://www.mouser.com/Circuit-Protectio ... Mgod-g0A6g

HTH

T2


Thanks, I checked it out but they don't have the one I'm looking for. Rare fuse I guess.


Have you tried your local Radio Shack? They always seem to have those hard to find items like this.

T2

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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Tue Feb 12, 2013 6:52 pm 
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T2Stratman wrote:
Bedlam9 wrote:
T2Stratman wrote:
Ahem...Google is your friend. I spent two minutes and found this...and plenty others.

http://www.mouser.com/Circuit-Protectio ... Mgod-g0A6g

HTH

T2


Thanks, I checked it out but they don't have the one I'm looking for. Rare fuse I guess.


Have you tried your local Radio Shack? They always seem to have those hard to find items like this.

T2


A 0.5 amp, 250 volt fuse is the same as a 1 amp, 125 volt fuse. :idea:

http://www.radioshack.com/product/index ... d=2102746#

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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Tue Feb 12, 2013 8:24 pm 
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I'll check out the shack, and thanks for the advice, Bill, I'll keep that in mind.


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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Thu Mar 07, 2013 1:33 pm 
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bluesky636 wrote:

A 0.5 amp, 250 volt fuse is the same as a 1 amp, 125 volt fuse. :idea:

http://www.radioshack.com/product/index ... d=2102746#


No! Bad advice! Fuses are designed to open when the current rating is exceeded, so a 1 amp fuse gets replaced with a 1 amp fuse, always. Oh, you won't hurt anything putting a 0.5 amp fuse in, but that means it might blow when it's working normally, which you don't want.

The voltage rating of the fuse is the maximum working voltage the fuse can have across it if it does blow. This is to ensure the fuse does not arc over if it blows. It is perfectly acceptable to replace a 1 amp, 125 volt fuse with a 1 amp, 250 volt fuse, provided the working voltage does not exceed 250 volts. Putting a fuse with a higher current rating in is NOT acceptable though.

To the OP, the slow-blow type fuse is important. The surge when the unit is first turned on might be enough to momentarily exceed the fuse rating, so a slow-blow is designed to withstand this. If you put a normal (fast blow) fuse in, it might very well blow even if nothing is wrong. So, to answer your question, it is fine to put 250 volt, 1 amp, slow-blow fuse in.

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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Sun Oct 05, 2014 5:15 pm 
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Sparky Dave is exactly right and Bluesky636 is exactly wrong. what Bluesky says is true about power. .5 amp at 240 would be the same power as 1 amp at 120 however fuses are not rated for power. They are rated for current.

Warning: Major geek speak after this point! You have been warned!

When you look at the ratings for wire, the two things that they look at are Current and Distance for determining what gauge you need. Voltage isn't even part of the equation. Because of skin effect, Frequency can be but not, voltage. At 60HZ skin effect really doesn't matter so we don't look at it. At 30MHZ its a different matter.

The way to think of it is this. Current is exactly that. It's the size of the flow through a piece of wire. You can think of it as the number of electrons that go through a piece wire in a given time period. Voltage is the force that is pushing them. That is how badly they want to get from point A to point B. Work done is the product of these two factors. 1 amp of current will be the exact same number of electrons passing through our wire regardless of how much push there is to it. 1 amp at 10 volts will have passed the exact same number of electrons through the wire as 1 amp at 1000 volts. At 1000 volts there will be a whole heck of a lot more "push" behind they so they will A. be able to do more work and B. You will need stronger insulation to keep all the electrons in the wire.

The metals we use for wire have a funny property. They basically have no resistance below a threshold of current based on the size of there cross section. Above that threshold of current, it's resistance rises quickly causing heat. Some wires are built to do this like tungsten. A cold light bulb has almost no resistance. As you increase the current through it, It's resistance rises quickly creating heat and in the case of a light bulb, light. It produces more heat than light. In the case of a fuse, The heat quickly causes the wire to fail. It's all about distance and diameter and it has effectively nothing to do with voltage.

I hope this help bring some clarity to the subject.

Archie


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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Mon Oct 06, 2014 6:47 am 
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Thanks, for the nice explanation. This is the reason a 20 amp glass fuse from a car (12 volt DC rated) will destroy an amp running 120 or 220VAC.

:cry:


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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Mon Oct 06, 2014 12:21 pm 
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Well technically speaking, Two things, 1st. Auto motive stuff is usually rated for 32 volts. That allows it to be used in 24 volt systems as well. In truth 12 volt systems really run at about 14 volts and 24 volt systems run at about 28 volts. Sometimes even a little higher thus the 32 volt rating. 2nd. A 20 amp 32 volt fuse should not destroy the amp but, rather if something fails in the amp, It will not prevent the amp from quite completely destroying itself and possibly tripping a breaker. Oh and it could arc over at the fuse depending on the fuse holder and cause yet more fun.

I know I'm being nitpicky again

Sorry

Archie


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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Mon Oct 06, 2014 2:40 pm 
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" A 20 amp 32 volt fuse should not destroy the amp but, rather if something fails in the amp, It will not prevent the amp from quite completely destroying itself and possibly tripping a breaker. Oh and it could arc over at the fuse depending on the fuse holder and cause yet more fun. "

Yeah, that is what I meant. A fuse is only a piece of wire. So, by itself won't destroy an amp, if properly placed. But, I've worked on more than a few fried amps... that had 20amp car fuses placed into the fuse holder. Cooked trannies and popped caps. --- where the fuse failed to do its job.


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 Post subject: Re: Fuse for 1975 Silverface Champ?
PostPosted: Wed Oct 08, 2014 10:13 am 
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Nice info here. Thanks, sparkydave, Archieaa1,
mud


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