can't identify glass fuse

Thread Starter

Daan Lageschaar

Joined Jul 8, 2019
36
Hi there :)

I have a speaker which has a fuse in it, but that fuse blew unfortunately.
Now I wanna get a new fuse but I have no clue how to identify it. It only has the letters R S and B on it (not next to eachother) and the number 4.
The speaker the fuse came from is a Wharfedale EVP S15 speaker.

I hope you can help me :D

Thanks in advance,
-Daan

This is how the fuse looks:
WhatsApp Image 2019-07-07 at 19.31.06 (1).jpeg WhatsApp Image 2019-07-07 at 19.31.06.jpeg
 

kubeek

Joined Sep 20, 2005
5,731
Typically speakers have small light bulbs to limit the current, I heard them called sufit lamps, but I am not sure if that is the correct term in english.
 

Thread Starter

Daan Lageschaar

Joined Jul 8, 2019
36
It does not appear to be blown.
probably a 250v - 4A fuse.
Thanks for your reply :)

I should maybe have added this to the original question, but the speaker gets it's power from the amplifier which outputs somewhere around 40v I think. Or in other words, it's not directly connected to a power outlet so I don't think it'd be a 250v fuse, or am I wrong about that?

ps. it is blown because when I tap it with my finger you can see it's not connected anymore
 

Thread Starter

Daan Lageschaar

Joined Jul 8, 2019
36
Typically speakers have small light bulbs to limit the current, I heard them called sufit lamps, but I am not sure if that is the correct term in english.
I just looked up a datasheet ( http://www.premier-acoustic.co.uk/PDFPAGES/101-149/PREMIER_-128.pdf ) and it does seem to be a light bulb, but I looked over it because I was looking for the word fuse.

Do you know how those lightbulbs are called in other languages? maybe that could help me out more.
 

MrChips

Joined Oct 2, 2009
21,687
It is a lightbulb, not a fuse.
It is placed in series with a loudspeaker to protect the speaker.
When the amp power output is too high the bulb lights up and its resistance increases dramatically. This will restrict the current to the speaker.
I have seen this happen when the mic/amp hits feedback mode.
 

Thread Starter

Daan Lageschaar

Joined Jul 8, 2019
36
It is a lightbulb, not a fuse.
It is placed in series with a loudspeaker to protect the speaker.
When the amp power output is too high the bulb lights up and its resistance increases dramatically. This will restrict the current to the speaker.
I have seen this happen when the mic/amp hits feedback mode.
I have found the replacements, BUT there are 2 versions a red dot version and a blue dot version:
https://www.djsupplies.co.uk/collections/spare-parts/products/crossoverfusebluewharfedale

https://www.djsupplies.co.uk/collections/spare-parts/products/crossoverfuseredwharfedale

does anyone know if there is a standardized difference between red and blue?
 

cmartinez

Joined Jan 17, 2007
7,063
When you do find a replacement, make sure you do not handle it with your bare fingers! ... the oils and grease in your fingers (there's always a trace) will make the glass heat unevenly when the bulb is at work, and quite possibly crack it.
If you've already made that mistake, make sure to clean the whole bulb (wearing gloves) thoroughly using a de-greaser (such as Windex) and some gauze.
 

MrChips

Joined Oct 2, 2009
21,687
You don't have to be so critical with how you handle the bulb.
This precaution is required when installing high intensity halogen bulbs. Your speaker "fuse" will never get so hot.
 
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