Is this a time-delay or 'slo-blo' fuse?

P

phaeton

Guest
I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?

Thanks for any help. I want to make sure to replace it with the exact
match.

-ph
 
phaeton wrote:

I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?

Thanks for any help. I want to make sure to replace it with the exact
match.

-ph

normally, if you look at the board they're in, there is some
Click to expand...
indication of a "S" , like "SF1"
if not,.
then look at what remains of the fuse.
if the wire is straight, it's a fast blow, if it's
got bends in it. It most likely is a slow blow.

In any case, depending on what the device does.
I would just put in a slow blow.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
 
On Sep 16, 5:41 pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
phaeton wrote:
I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?

Thanks for any help. I want to make sure to replace it with the exact
match.

-ph

normally, if you look at the board they're in, there is some
indication of a "S" , like "SF1"
if not,.
then look at what remains of the fuse.
if the wire is straight, it's a fast blow, if it's
got bends in it. It most likely is a slow blow.

In any case, depending on what the device does.
I would just put in a slow blow.

--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.http://webpages.charter.net/jamie_5
Click to expand...

Thanks for the reply. In addition to the usual "Replace only with
same type and rating" it does have a small marking of:

115V~S315mA 250V
230V~T160mA 250V

Would I then assume that in North America (where I am) it would be a
slow-blow? Looking at what's left of the fuse itself, the lead might
actually be straight. Is a slow-blow the 'safe' bet in any case?

The circuit is a solid-state guitar amp. Most tube-fired guitar amps
say "replace only with slo-blo(tm) fuse".

Thanks

-ph
 
On Sun, 16 Sep 2007 23:52:01 +0000, phaeton wrote:

On Sep 16, 5:41 pm, Jamie
jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
phaeton wrote:
I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?

Thanks for any help. I want to make sure to replace it with the exact
match.

-ph

normally, if you look at the board they're in, there is some
indication of a "S" , like "SF1"
if not,.
then look at what remains of the fuse.
if the wire is straight, it's a fast blow, if it's
got bends in it. It most likely is a slow blow.

In any case, depending on what the device does.
I would just put in a slow blow.

--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.http://webpages.charter.net/jamie_5


Thanks for the reply. In addition to the usual "Replace only with
same type and rating" it does have a small marking of:

115V~S315mA 250V
230V~T160mA 250V

Would I then assume that in North America (where I am) it would be a
slow-blow? Looking at what's left of the fuse itself, the lead might
actually be straight. Is a slow-blow the 'safe' bet in any case?

The circuit is a solid-state guitar amp. Most tube-fired guitar amps
say "replace only with slo-blo(tm) fuse".

Thanks
Click to expand...
The resistor dampens some of the the current inrush when the device is
powered up. SS amps have a rather quick current inrush whereas a tube amp
ramps off more slowly hence the need for the slow blow.
 
"phaeton"
I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?
Click to expand...

** Correct.

But there are lots of ways to skin cats and make slow acting fuses - the
ones which incorporate a small resistor are precise, but only come in low
amp values.

Other types have a coil spring that pulls a soldered link apart.

Some look just like a normal, straight wire fuse.

Most carry the letter " T " ( for the German word " trage " ) after the
amp figure, which BTW is the never fail current.



....... Phil
 
"Meat Plow"


The resistor dampens some of the the current inrush when the device is
powered up.
Click to expand...

** Not of any consequence with a 315mA fuse.


SS amps have a rather quick current inrush whereas a tube amp
ramps off more slowly hence the need for the slow blow.
Click to expand...

** Total drivel.

Both types have similar, transformer based PSUs and so have similar inrush
surges.

For a given power rating, the tube amp will have a larger PSU and so a worse
surge.

The main part of the surge lasts only one cycle of the AC supply frequency -
in both cases.



........ Phil
 
phaeton wrote:

On Sep 16, 5:41 pm, Jamie
jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

phaeton wrote:

I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?

Thanks for any help. I want to make sure to replace it with the exact
match.

-ph

normally, if you look at the board they're in, there is some
indication of a "S" , like "SF1"
if not,.
then look at what remains of the fuse.
if the wire is straight, it's a fast blow, if it's
got bends in it. It most likely is a slow blow.

In any case, depending on what the device does.
I would just put in a slow blow.

--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.http://webpages.charter.net/jamie_5



Thanks for the reply. In addition to the usual "Replace only with
same type and rating" it does have a small marking of:

115V~S315mA 250V
230V~T160mA 250V

Would I then assume that in North America (where I am) it would be a
slow-blow? Looking at what's left of the fuse itself, the lead might
actually be straight. Is a slow-blow the 'safe' bet in any case?

The circuit is a solid-state guitar amp. Most tube-fired guitar amps
say "replace only with slo-blo(tm) fuse".

Thanks

-ph

yes, you assumed correctly.
Click to expand...


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
 
phaeton wrote:

I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?

Thanks for any help. I want to make sure to replace it with the exact
match.
Click to expand...
IEC style fuses (such as the 20x5mm type) should have a 'speed' rating on one of
the end caps.

The most popular are T (trage) for 'slow blow' and F(flink) for fast (normal)
blow. FF (superfast) types are typically used for semiconductor protection but
are rare as are 'M' types.

The cap will probably say T315mA.

It isn't actually a US 'slo-blo' type since US fuse specs aren't the same as the
international IEC ones. However if you ask for a T315mA to IEC spec you're
covered anyway.

Graham
 
phaeton wrote:

Thanks for the reply. In addition to the usual "Replace only with
same type and rating" it does have a small marking of:

115V~S315mA 250V
Click to expand...
Hmmm ... S ?

That's a new one on me. Most likely it does mean slow blow but I've never
encountered such a marking before. Possibly an Americanisation.

Graham
 
On Sep 16, 8:40 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:
phaeton wrote:
Thanks for the reply. In addition to the usual "Replace only with
same type and rating" it does have a small marking of:

115V~S315mA 250V

Hmmm ... S ?

That's a new one on me. Most likely it does mean slow blow but I've never
encountered such a marking before. Possibly an Americanisation.

Graham
Click to expand...
on one cap the fuse itself says "(SA) 51S" followed by three circles
arranged in a triangular pattern. The "(SA)" is stylized, and my
guess is it's a manufacturer logo. The other cap has the "250V 315mA"
followed by the three circle in tri-pattern. I see no T.

Not sure how I'd take a pic of this, tho. it's pretty small.
 
Eeyore wrote:

phaeton wrote:


Thanks for the reply. In addition to the usual "Replace only with
same type and rating" it does have a small marking of:

115V~S315mA 250V


Hmmm ... S ?

That's a new one on me. Most likely it does mean slow blow but I've never
encountered such a marking before. Possibly an Americanisation.

Graham

Yup, anything that is out of place with you has to be American!
Click to expand...


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
 
On Sun, 16 Sep 2007 21:21:12 +0000, phaeton wrote:

I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?

Thanks for any help. I want to make sure to replace it with the exact
match.
Click to expand...
They're the same thing - it's just that somebody copyrighted the
name "slo-blo" so they can't use it. ;-)

Cheers!
Rich
 
Rich Grise wrote:

phaeton wrote:

I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?

Thanks for any help. I want to make sure to replace it with the exact
match.

They're the same thing - it's just that somebody copyrighted the
name "slo-blo" so they can't use it. ;-)
Click to expand...
Conceptually the same thing but US slo-blo fuses do in fact have slightly
different fusing chracteristics to international IEC T types.

Graham
 
Eeyore wrote:

Rich Grise wrote:


phaeton wrote:


I have a blown fuse here, 5mm x 20mm. It is marked 250v 315ma. On
the inside, it has what looks like a metal film resistor connected in
series with (what used to be) the element. Mouser has a fuse with the
above specs available, but also with the choice of 'fast acting' and
'time delay'. Pictures in the datasheets are the same for both.

I assume that this is a time delay fuse, hence the resistor?

Thanks for any help. I want to make sure to replace it with the exact
match.

They're the same thing - it's just that somebody copyrighted the
name "slo-blo" so they can't use it. ;-)


Conceptually the same thing but US slo-blo fuses do in fact have slightly
different fusing chracteristics to international IEC T types.

Graham

THere you go again. Using the US as the displaced member of the
Click to expand...
world.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
 
Jamie wrote:
Eeyore wrote:

Conceptually the same thing but US slo-blo fuses do in fact have slightly
different fusing chracteristics to international IEC T types.

THere you go again. Using the US as the displaced member of the
world.
Click to expand...

What do you expect from a 'Donkey' that rarely gets a glimpse of the
world outside of his filthy stall, behind the barn?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
Thanks for all the help, everyone!

I've got the replacement on the way, and I'm confident that it's the
right thing.

-phaeton
 
On 17 Sep, 03:22, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

Yup, anything that is out of place with you has to be American!
Click to expand...
And with me.
 
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