Discussion:
Melted Fuse
(too old to reply)
Simon Dean
2005-12-15 16:41:34 UTC
Permalink
WEll, my amplifier has been cutting out recently.


I have a JBL 75.4 and it has been rock solid ever since I got Rush's new
R30 CD/DVD combo. The amp was giving surprisingly, rock solid
performance, and I was able to turn the volume up another couple of
notches without distortion.

Over the past couple of days though, things had been cutting out.
Thought it might be over heating.

But today, having a look, no heat, no power lights, occasionally a red
light would flash, but that was very rare. Fuses look fine, until I look
at the main wire from the battery at the engine compartment.

The fuse, and fuse holder (except for the cap), is quite literally
melted. Trying to get the fuse out, and the thing is cracking as I try.
So Im going to leave it.

I can't remember if it was the 8 grade, or 4 grade wire, it's not
exactly huge, so I think it was 8. But should be plenty good enough to
power this AMP and the rather small speakers of 4x6" in the front and
5.25" in the rear...

So what could have caused the fuse to melt?

Thanks
Simon
Jon
2005-12-19 15:03:48 UTC
Permalink
I suspect you must have a short somewhere. What size fuse have you
got? This should have blown long before things got that hot.

My 75.4 is connected with 8 guage wire and a 60A fuse. The holder
never gets warm.

I guess the only other thing that could do it is if your fuse had
worked its way loose but not fully disconnected. That way you would
have a crap connection between your cable and fuse. Under high load
that would mean upto 60A trying to rush through a small wire,
resulting in heat build up. Is there any visible evidence of this in
your melted heap of plastic?

Jon


On Thu, 15 Dec 2005 16:41:34 +0000, Simon Dean
Post by Simon Dean
WEll, my amplifier has been cutting out recently.
I have a JBL 75.4 and it has been rock solid ever since I got Rush's new
R30 CD/DVD combo. The amp was giving surprisingly, rock solid
performance, and I was able to turn the volume up another couple of
notches without distortion.
Over the past couple of days though, things had been cutting out.
Thought it might be over heating.
But today, having a look, no heat, no power lights, occasionally a red
light would flash, but that was very rare. Fuses look fine, until I look
at the main wire from the battery at the engine compartment.
The fuse, and fuse holder (except for the cap), is quite literally
melted. Trying to get the fuse out, and the thing is cracking as I try.
So Im going to leave it.
I can't remember if it was the 8 grade, or 4 grade wire, it's not
exactly huge, so I think it was 8. But should be plenty good enough to
power this AMP and the rather small speakers of 4x6" in the front and
5.25" in the rear...
So what could have caused the fuse to melt?
Thanks
Simon
Simon Dean
2005-12-20 07:12:54 UTC
Permalink
Thanks for the reply.

It was a standard blade 30 AMP fuse that came with the "Toxic" 8 gauge
wiring kit.

As far as I could tell, the fuse was securely fastened in. I couldn't
move it by hand. I removed the fuse, and the amplifier wouldn't work, so
no "short" in the fuse holder.

And I've just changed the fuse for a 60 AMP and a big bloody fuse
holder. Seems OK so far, no problems.
Post by Jon
I suspect you must have a short somewhere. What size fuse have you
got? This should have blown long before things got that hot.
My 75.4 is connected with 8 guage wire and a 60A fuse. The holder
never gets warm.
I guess the only other thing that could do it is if your fuse had
worked its way loose but not fully disconnected. That way you would
have a crap connection between your cable and fuse. Under high load
that would mean upto 60A trying to rush through a small wire,
resulting in heat build up. Is there any visible evidence of this in
your melted heap of plastic?
Jon
On Thu, 15 Dec 2005 16:41:34 +0000, Simon Dean
Post by Simon Dean
WEll, my amplifier has been cutting out recently.
I have a JBL 75.4 and it has been rock solid ever since I got
Rush's new R30 CD/DVD combo. The amp was giving surprisingly, rock
solid performance, and I was able to turn the volume up another
couple of notches without distortion.
Over the past couple of days though, things had been cutting out.
Thought it might be over heating.
But today, having a look, no heat, no power lights, occasionally a
red light would flash, but that was very rare. Fuses look fine,
until I look at the main wire from the battery at the engine
compartment.
The fuse, and fuse holder (except for the cap), is quite literally
melted. Trying to get the fuse out, and the thing is cracking as I
try. So Im going to leave it.
I can't remember if it was the 8 grade, or 4 grade wire, it's not
exactly huge, so I think it was 8. But should be plenty good enough
to power this AMP and the rather small speakers of 4x6" in the
front and 5.25" in the rear...
So what could have caused the fuse to melt?
Thanks Simon
Jon
2005-12-20 07:57:19 UTC
Permalink
IMHO a 30A fuse is not big enough for that amp. Max wattage is 568W
for noise delivery + that of internal workings. Even 568W @ 12V =
47.3A.

So to be safe at full power you should have a 50A fuse, nearest
available therefore = 60A.

By enlarge blades are either in or out. I suspect your problem was
simply a 30A fuse running at 99% capacity for a sustained period.

Jon


On Tue, 20 Dec 2005 07:12:54 +0000, Simon Dean
Post by Simon Dean
Thanks for the reply.
It was a standard blade 30 AMP fuse that came with the "Toxic" 8 gauge
wiring kit.
As far as I could tell, the fuse was securely fastened in. I couldn't
move it by hand. I removed the fuse, and the amplifier wouldn't work, so
no "short" in the fuse holder.
And I've just changed the fuse for a 60 AMP and a big bloody fuse
holder. Seems OK so far, no problems.
Post by Jon
I suspect you must have a short somewhere. What size fuse have you
got? This should have blown long before things got that hot.
My 75.4 is connected with 8 guage wire and a 60A fuse. The holder
never gets warm.
I guess the only other thing that could do it is if your fuse had
worked its way loose but not fully disconnected. That way you would
have a crap connection between your cable and fuse. Under high load
that would mean upto 60A trying to rush through a small wire,
resulting in heat build up. Is there any visible evidence of this in
your melted heap of plastic?
Jon
On Thu, 15 Dec 2005 16:41:34 +0000, Simon Dean
Post by Simon Dean
WEll, my amplifier has been cutting out recently.
I have a JBL 75.4 and it has been rock solid ever since I got
Rush's new R30 CD/DVD combo. The amp was giving surprisingly, rock
solid performance, and I was able to turn the volume up another
couple of notches without distortion.
Over the past couple of days though, things had been cutting out.
Thought it might be over heating.
But today, having a look, no heat, no power lights, occasionally a
red light would flash, but that was very rare. Fuses look fine,
until I look at the main wire from the battery at the engine
compartment.
The fuse, and fuse holder (except for the cap), is quite literally
melted. Trying to get the fuse out, and the thing is cracking as I
try. So Im going to leave it.
I can't remember if it was the 8 grade, or 4 grade wire, it's not
exactly huge, so I think it was 8. But should be plenty good enough
to power this AMP and the rather small speakers of 4x6" in the
front and 5.25" in the rear...
So what could have caused the fuse to melt?
Thanks Simon
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