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Fuses?!?
#11
(04-12-2019, 07:27 AM)Overmind Wrote: Voltage range is not too relevant in a fuse. It's the current that matters.

Maybe the amplifier was designed for a lower voltage ? In that case, if powered from more, it will burn no matter the fuse you use.

The voltage range matters from a operating design and saftey standpoint.  There is a reason breakers, fuses, and other saftey devices have a max voltage rating.  

The OP did use a fuse which was under rated for the application, it would be unreasonable to expect it to do its job.  It becomes unpredictable and may not function outside of its operating range.  Arching is most common occurrence.

Either way, I suspect the fuse might have nothing to do with the failure with the amp.
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#12
(04-12-2019, 01:18 PM)Redpacket Wrote: So it seems shorted output is the likely cause.
As often happens, the output stage "blew to protect the fuse"! Ie the junctions in the transistors are less thermal mass than the fuse & blow first.
Like daromer suggests maybe check the spec for the recommended fuse.
Using proper connectors like XLR or "speakon" speaker connectors helps avoid shorts.

There are no other connectors on the board than the terminals. But I'll secure it better next time.

Sooo. I guess I'll have to go for a smaller fuse
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#13
Were you pushing the amp hard when it failed?

I looked at the product... it seems pretty cool. I am also a customer of parts express and find them to be a good reliable vendor. Perhaps reach out to them, maybe you got a defective item.
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#14
To get back on track. Im almost sure I shorted the connection between the terminals. I am surprised that the fuse didn't burn and would like to know where you get fuses when working with 48V?

Thanks
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#15
(04-12-2019, 04:18 PM)Crimp Daddy Wrote:
(04-12-2019, 07:27 AM)Overmind Wrote: Voltage range is not too relevant in a fuse. It's the current that matters.

Maybe the amplifier was designed for a lower voltage ? In that case, if powered from more, it will burn no matter the fuse you use.

The voltage range matters from a operating design and saftey standpoint.  There is a reason breakers, fuses, and other saftey devices have a max voltage rating. 
That is correct. Fuses have a rating for Voltage, it comes into question when the fuse tries to break a current. That is easier on AC than on DC, when you have both parameters the DC rating is most probably lower. AC does help to extinguish an arc, with DC you have just to use enough current (and something like 100 Volt) and you can draw an arc nearly endless, means several centimeters or more.
Especially said, the current breaking value of the fuse is not interfered by DC, it just might not be able to break a current when it tries. And the arc which stays has a HOT potential for damage just by heat.

Quote:The OP did use a fuse which was under rated for the application, it would be unreasonable to expect it to do its job.  It becomes unpredictable and may not function outside of its operating range.  Arching is most common occurrence.

I have looked up the typical (european) car fuse, do you have the same in US ?
It is rated for 40 V.
So you are formally correct again, that voltage is exceeded by the OPs application. It might have still worked, because such a rating surely has a safety area,  in that case as ALL those car fuses are rated the same, i suggest the lower amps have a little better switching capability.
But alas, it has not gone that far that the fuse even tried separating/arcing.
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#16
(04-12-2019, 01:11 PM)Cherry67 Wrote: Its nice that all are discussing the fuse, but since the fuse did NOT blow it had not anything to do with his fire. Whatever this caused, its not the fuse.

Is a Class D amplifier, what about the speakers, have they been connected, is that possibly necessary ?

Ops, first read then write Big Grin Big Grin

You are correct, although the fuse probably should have blown. The idea of a fuse is to prevent fire in case of failure.
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#17
If you're trying to protect electronics you need fuses with an amp rating & time constant short enough to blow first before the transistor junction melts, eg "fast blow".
The 3AG type fuses can do 48V & fast blow.
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