# Will replacing 2amp 125v with 2amp 250v work?



## Yoyizit (Jul 11, 2008)

roycar71 said:


> I have Yamaha amplifier that will not come on and want to rule out fuses even tho they don't seem damaged. I have googled and can not find 2amp 125V fuse. All i find is 2amp 250V fuse. Will this work instead?


The 'clearing time' will be longer but I don't think that will make a difference here.
Check the fuse with an ohmmeter.
For fixing, it will help if you have a DVM and can post a schematic.


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## micromind (Mar 9, 2008)

Any fuse can be replaced with one of a higher voltage rating. The voltage rating of a fuse is a maximum. 

A 250 volt fuse will work just fine.

Rob


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## roycar71 (Sep 12, 2009)

Can not find schmatics but here is pics of inside even tho that may not help. I do not see any chard parts.


Yoyizit said:


> The 'clearing time' will be longer but I don't think that will make a difference here.
> Check the fuse with an ohmmeter.
> For fixing, it will help if you have a DVM and can post a schematic.


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## Yoyizit (Jul 11, 2008)

If you don't see a cracked or charred component, I think you'll need a bench full of test equip., a head full of electronic theory, a schematic and at least one whole day to do this, unless you can find someone on the Internet who had the same problem with the same amp. and solved it.

On top of that, some schematic booklets [which look like street maps of Manhattan] cost $50 and the bad part, if you find it, will also be costly. And if you don't find the root cause the new part will not last long.

Since the output stages are stressed, I'd start looking there.

Or get several bids on fixing it.

I have the equip., etc., and I still dread puzzling through one of these. And if you short something out while you're chasing signals you've got more work on your hands.

If you opt to sell it you can use the Effros method; it doesn't much matter if it works, with this selling technique. 

Sorry. . .


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## roycar71 (Sep 12, 2009)

Before i decide to go through more work. I will try changing out fuses. http://www.fixitclub.com/Parts_Components/Fuse.shtml?page=1 says 
"sometimes fuses get worn out". I will post my results once i change out fuses.


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## user62257 (Sep 12, 2009)

roycar71 

make sure you use a fuse that are rated at 125 VAC and not 250 VAC.

Bussman makes a 4 amp. fuse @ 125 VAC.

I'm not sure what thec orrect amp. fuse is in your case, but fuses can be found rated @ 125 VAC.

Just use google, try Buss fuses and Bussman fuse, Little Fuses, etc.


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## micromind (Mar 9, 2008)

4X, why? 

I've been a commercial/industrial electrician for 19 years, and this is the first time I've ever heard that you couldn't use a fuse with a higher voltage rating. 

Could you explain the negative effects of such use? 

Rob


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## Yoyizit (Jul 11, 2008)

micromind said:


> Could you explain the negative effects of such use?


Yes, this I have to hear. 
If it's a clearing time consideration, usually they want a slower clearing time to avoid having circuit inductance generate unduly high -L(ΔI/ΔT) spikes.


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## user62257 (Sep 12, 2009)

*NO! *

But I will tell what I seen done. I once saw someone use an auto fuse
that was the same size as the one that blew out, only the voltage rating
of the fuse was to low, and the replacement blow out. Yes what does
that have to do with what your talking about. It doen't. But it shape
my mind so that I would only use what the MFG. had install for a fuse.

I'm voicing my opinion only in my Post. And I am not rejecting your suggesting.

I sure you could use a 250 VAC fuse, and it would work.

But I would try to go with what the MFG. install for the original fuse.

So if your thinking I am saying he should not do what you have suggested, then mis-spoke. I was just stating my own opinion.

Final, if the his equipment bears a UL Label, does changing the fuse
to 250 VAC void the UL listing? That all folks. (humor)

I don't play with trains, I am not am engineer (humor)


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## micromind (Mar 9, 2008)

Using a fuse with a higher voltage rating than the actual voltage applied does not void a UL listing. 

Fuses (and their holders) are UL listed for a maximum voltage, not a minimum. 

Certainly, if a fuse with a lower voltage rating is used, and it is subjected to a short circuit, there's a very good possibility of an explosion. 

Rob


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## Yoyizit (Jul 11, 2008)

micromind said:


> Certainly, if a fuse with a lower voltage rating is used, and it is subjected to a short circuit, there's a very good possibility of an explosion.
> 
> Rob


That's the interrupting rating; I have seen two fuses in series, one to act quickly, one to quench the arc without exploding. 
One version of the Simpson 260 used this technique. 

F1 Fuse, 1A, 250V; 3AG (1-1/4” x 1/4”) 1-112507 
Quick acting (Littlefuse Type 312001) 

F2 Fuse, 2A, 600V, Littlefuse Type BLS or 
2A, 500V, Bussman Type BBS. 

Voltage rating probably does correlate well with interrupting rating.

Low voltage fuses in higher voltage equip. quench the arc too quickly and so have normal circuit inductances cause voltage spikes that can damage sensitive electronics. Vacuum tubes probably don't care about these spikes.


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## balkoths (Jun 12, 2013)

Hello I had this same thing on my sansui receiver last month and what I was told if you go up in voltage you must go down in amps. So mine was the same as your 125 volt 2 amp, so I replaced it with a 250 volt 1 amp fuse and it seemed to working fine.


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## Gac66610 (Aug 25, 2012)

balkoths said:


> Hello I had this same thing on my sansui receiver last month and what I was told if you go up in voltage you must go down in amps. So mine was the same as your 125 volt 2 amp, so I replaced it with a 250 volt 1 amp fuse and it seemed to working fine.


Well, if he hasn't fixed this or replaced it in the last _4 years_ he'll be glad to hear


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## AllanJ (Nov 24, 2007)

A 250 volt fuse of the same amperage and same time delay characteristics will work just as well as a 125 volt fuse in this 125 volt application.

But don't use a lower voltage rating like 12 volts; the fuse after blowing could "arc over" inside from the higher voltage because internal parts are closer together.


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## joed (Mar 13, 2005)

You can go up in voltage on a fuse but not down.\
Here is why as I understand it.

Every time you open a circuit you create an arc. The larger the voltage the larger the gap the arc can jump. A gap too small and the arc will not break and you essentially have a welder. A 12 volt auto fuse can not be used in 125 volt AC application as the arc may never break until the fuse itself disintegrates. If your device needs a 2 amp 125 volt fuse there is no problem using a 2 amp 250 volt fuse. The higher voltage rating means the gap will be fine at 125 volts. You must always use the same amperage, no matter what the voltage.


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## dmxtothemax (Oct 26, 2010)

Those yamaha power amps have extensive protection circuits in them,
So if everything is not 100%, then the protection circuit will do it's job
and not allow the unit to come out of stand by mode.
Unless you have a proper circuit diagram / service manual
your chances are very slim indeed,
better off taking it to an electronics repairer,
as they really are quite complex.


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## sirsparksalot (Oct 16, 2010)

Gac66610 said:


> Well, if he hasn't fixed this or replaced it in the last _4 years_ he'll be glad to hear


:laughing::laughing::laughing:


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## Kyle_in_rure (Feb 1, 2013)

sirsparksalot said:


> :laughing::laughing::laughing:


:wallbash:

I hate it when I want to reply to the OP of a thread but then discover it is years old.....


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