# Sansui G4700 Receiver HELP! Fuse Blowing



## thend2000 (Jun 11, 2015)

I have a Sansui G 4700 from the 70's and i had it working perfectly and its in great shape, but one day the fuse blew. Now, the fuse i pulled out of it was a buss glass 125v 5a. I can't seem to find a 125v so i keep changing it with a 250v 5a hoping that it will work but every time i switch it on it turns on and immediately blows. is this because I'm using a 250v? or can it be something else? I feel like it could be an additional problem but the 250v fuse is certainly not helping anything. I also would like to know if anyone knows where i can find a buss glass fuse 125v 5a 1 1/4 inch. I'm very new at this and would grately appreciate any help at all! Thank you all very much and have a great week!


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## joeten (Dec 4, 2008)

Hi and welcome to TSF, have a look here https://www.google.co.uk/search?q=b...-8&oe=utf-8&gws_rd=cr&ei=wQp6VYKaNYLjUfTpgvgI I don't the product but there is a video here and manuals which may provide some help and ideas https://www.google.co.uk/search?q=s...-8&oe=utf-8&gws_rd=cr&ei=DAt6VYm8HMXcUavogYAJ
From what I see here it may be down to the speakers Sansui G 4700 - AudioKarma.org Home Audio Stereo Discussion Forums


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## Panther063 (Jul 13, 2009)

The fuse will not blow because it has a higher voltage rating, it would if the situation was reversed and input voltage was higher than the fuses rating.


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## Bill_Bright (Dec 17, 2004)

> I can't seem to find a 125v so i keep changing it with a 250v 5a hoping that it will work but every time i switch it on it turns on and immediately blows. is this because I'm using a 250v?


No. It is blowing because another component in the circuit has shorted and causing too much current (over 5A in this case) to flow through the circuit, heating up the fusible link beyond its capacity, thus blowing the fuse. 

The voltage rating of the fuse has absolutely nothing to do with how much current it takes to blow the fuse. That is the same regardless the voltage. 

The voltage rating of the fuse has everything to do with what happens AFTER the fuse blows. 

The difference between a 125V and 250V fuse is the "fusible link" inside the fuse is physically longer with the 250V fuse. This means when the link inside burns/melts away, the resulting gap between the end "terminals" it longer in a 250V fuse than it will be in a blown 125V fuse. 

That matters because larger the gap, the higher the voltage potentials must be to arc (jump across) the gap. 

You can use a 250V 5A fuse in place of a 125V 5A but you can't use a 32V 5A fuse because the remaining gap between the two end terminals will be too small and leaving the potential for the voltage in the circuit to arc across the gap in the 32V fuse - keeping the circuit alive. Not good!

So the larger the gap, the higher the voltage potential must be to jump across it. For this reason, it is a safer alternative to substitute a 250V fuse in place of a 125V fuse while having no impact on the current rating of the fuse. 

Because it is safer without changing the current rating, and because much of the world uses 220-240VAC, it is cheaper for fuse makers to make and electronics supply channels to carry 250V fuses only. So 125V fuses are harder, if not impossible to find anymore.


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