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Fast blow speaker fuses


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Hi there;

I know I repeat myself with fusing discussions.

At least I'm trying to keep this on topic.

I have not ever seen Littlefuse FLM slow blow delayed fuses in any store here.

Bussmann FNM is the only brand AR mentioned and is the only type I have come across thus far.

These are the equivalent fuses from two different manufacturers.

The Bussmann fuses are becoming scarcer and more expensive as time goes along.

At this point I feel that fast blow 1/4" x 1 1/4" fuses, in an open style fuseholder, should be considered as an alternative.

Also at about 10% of the cost of the slow blow fuses.

As far as AR speakers are concerned, AR only ever mentioned FNM slow blow, never fast blow fuses, so we need to start from scratch with a fuse standard for today.

Heath/Heathkit/AR AS-103/AS103A used a chassis mounted, poor idea because of heat containment, but much better than no fuse, 3 amp fast blow fuse.

Advent recommended an FNM 8/10 amp slow blow fuse.

Dynaco recommended a 1 amp fast blow for the A-10, A-25, A-35 and 1 1/2 amp fast blow fuse for the A-50.

Other than this we are on our own to arrive at a safe value.

Obviously a fuse cannot be expected to protect the tweeter and woofers at the same level.

In my experience the tweeters are by far the weakest link, excepting the A-25.

With few exceptions, bi-amping will allow separate woofer, mid/highrange protection.

This option will at least allow the opportunity to use a fast blow fuse for the the mid/highrange and slow blow for the woofer.

I had used a 1 amp fast blow fuse in an open fuseholder with all of my speakers for many years.

I have never blown a driver on my own, yet.

There was a time when I saw 100's of blown woofers.

I am not very good with mathematical relationships.

Perhaps a few members can do a paralled relationship chart, there isn't more than a dozen fuse values, comparing the various AR slow blow fuse values and the equivalent fast blow fuse values.

This would benefit those on a tight budget at least, including myself.

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Hi again;

The actual number of equal fast blow fuses, 6 would be suitable for the following;

FNM 6/10 ex AR-4X

FNM 8/10 ex AR-5

FNM 1 1/4 ex AR-3A Re Heath/AR AS103/103A 3 amp fast blow about 1970

FNM 1 6/10 ex AR-10 pie

FNM 2 ex AR-LST

FNM 2 1/2 ex AR-LST listed on sheet L1631 4/74, if error then FNM 2

Of course these are 30 plus years old slow blow fuse ratings.

Perhaps we should de-rate them for our valuable old drivers of today.

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  • 2 weeks later...

>There seems to be a lot of interest by some people about

>fusing. Believe it or not there is a science to this which

>comes in a more generalized discussion of overcurrent

>protection of electrical devices. The principles are true for

>all electrical devices and are easy to understand. As with

>most things, the devil is in the details and getting the

>necessary data for any particular application such as fusing a

>particular piece of equipment may be difficult or impossible

>therefore requiring some educated guesses as the only

>alternative.

>

>ALL electrical devices have a maximum current they can

>tolerate before they are damaged. This current rating usually

>depends on how long it is applied for. The most common damage

>occurs from overheating as electrical devices turn some of the

>current which passes through them into heat. With

>loudspeakers, at least one other failure mode is over

>excursion which is pushing the linear motor beyond its

>mechanical limits. Regardless, there is a time/current

>failure curve for each device and it is usually drawn on log

>paper. The art and science of protecting devices from failure

>is to therefore put one or more devices in series with it

>which will interrupt the current BEFORE it reaches the time

>current failure curve of the device being protected. This is

>usually done with a combination of fast and slow blow fuses or

>in the case of very large circuit breakers, adjustments for

>short and long term trip settings. This is actually required

>for example in the startup of a large motor or the initial

>turn on of a transformer because if the circuit is interrupted

>by a single fast device which protects its longterm withstand

>current, it will blow every time on startup.

Conversely, if it's large enough to allow it to start up without

interruption, it will not protect it from long term overcurrent.

Therefore, a combination of fast and slow blow fuses in series is required for each device (speaker driver)to thoroughly protect it. Data for the time current interrupting characteristics for fuses are given by the manufacturer.

Hi there;

After reading this again for the umpteenth time, I must suggest that this is the best approach for an entire speaker system protection.

For one example only, an AR-3A speaker system, a FNM/FLM 1 1/4 or 1 amp slow blow fuse in series with an AGC 1 1/2 or 2 amp fast blow fuse also, both in open style fuseholders.

This will cover the need for separate fuseholders and individual driver fuses as best as possible.

It's up to you as the user to engineer a

>combination of two or more for each application to protect the

>drivers. Getting the time current withstand curve of the

>drivers is the hard part. There, I'm afraid you're on your

>own. The best you could do for old drivers like ARs and KLHs

>is to find comparable modern units for which their curves are

>known but because such things as insulating materials for

>voice coil wires are so different, that may not be possible.

>And yes, each driver is a separate problem. Good luck.

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It would be interesting to hear from readers who have ACTUALLY experienced a blown fuse (perhaps besides you Vern).

Did it prevent failure of the driver/s?

What kind of fuse were they using? FB or SB?

where was it installed?

what speaker were they protecting? and finally, what music/volume level was playing at the time of the fuse failure?

IF we get a few responses, we'll be able to see how similar (or dissimilar) they are. This information may help shed some light on the uniqueness of each speaker system.

If NO ONE responds with a real life experience, perhaps the fuses they may or may not have are either over sized, or they don't "pump up the volume" much.

It's all about the music

Carl

Carl's Custom Loudspeakers

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  • 4 weeks later...

>It would be interesting to hear from readers who have

>ACTUALLY experienced a blown fuse (perhaps besides you Vern).

.

.

.

It is now 3 weeks later and there has been no responses to Carl's question, as to whom has blown a speaker fuse.

.

.

.

My question today is, who has blown and how many and types of drivers because of no speaker fuses being used?

.

.

.

Was the damage by abuse or by accident?

.

.

.

.

How much did it cost you to replace the damaged drivers?

.

.

.

.

.

Since the damage was done to your drivers, have you started using speaker fuses?

.

.

.

.

http://www.electronicsurplus.com/ at present is a source, only for the Bussmann FNM 2 amp slow blow fuse at $1.50 US each.

.

.

.

.

For you AR-LST owners in particular, here is an opportunity to save some real money.

.

.

.

.

When they are gone, they are gone for good.

.

.

Vern

.

.

>

>Did it prevent failure of the driver/s?

>What kind of fuse were they using? FB or SB?

>

>where was it installed?

>what speaker were they protecting? and finally, what

>music/volume level was playing at the time of the fuse

>failure?

>

>IF we get a few responses, we'll be able to see how similar

>(or dissimilar) they are. This information may help shed some

>light on the uniqueness of each speaker system.

>

>If NO ONE responds with a real life experience, perhaps the

>fuses they may or may not have are either over sized, or they

>don't "pump up the volume" much.

>

>

>It's all about the music

>

>Carl

>Carl's Custom Loudspeakers

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  • 2 months later...
>It would be interesting to hear from readers who have

>ACTUALLY experienced a blown fuse (perhaps besides you Vern).

.

It is now 3 weeks later and there has been no responses to Carl's question, as to whom has blown a speaker fuse.

.

My question today is, who has blown and how many and types of drivers because of no speaker fuses being used?

.

Was the damage by abuse or by accident?

.

How much did it cost you to replace the damaged drivers?

.

Since the damage was done to your drivers, have you started using speaker fuses?

.

http://www.electronicsurplus.com/ at present is a source, only for the Bussmann FNM 2 amp slow blow fuse at $1.50 US each.

.

For you AR-LST owners in particular, here is an opportunity to save some real money.

.

When they are gone, they are gone for good.

.

Vern

.

.

>

>Did it prevent failure of the driver/s?

>What kind of fuse were they using? FB or SB?

>

>where was it installed?

>what speaker were they protecting? and finally, what

>music/volume level was playing at the time of the fuse

>failure?

>

>IF we get a few responses, we'll be able to see how similar

>(or dissimilar) they are. This information may help shed some

>light on the uniqueness of each speaker system.

>

>If NO ONE responds with a real life experience, perhaps the

>fuses they may or may not have are either over sized, or they

>don't "pump up the volume" much.

>

>

>It's all about the music

>

>Carl

>Carl's Custom Loudspeakers

Back again;

It appears that no-one here has blown a speaker driver or a fuse ever, judging by the overwhelming response to mine and Carl's question.

I will speaek no more about this subject.

Here is one manufacturers means of mounting open style fuseblocks for their one model speaker.

post-101040-1197418639.jpg

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Back again;

It appears that no-one here has blown a speaker driver or a fuse ever, judging by the overwhelming response to mine and Carl's question.

I will speaek no more about this subject.

Here is one manufacturers means of mounting open style fuseblocks for their one model speaker.

Those of us who have been around audio and/or electronics for any lenght of time understand the need for fusing, but I suspect this forum is frequented by a few newbies daily that never heard of the idea. Keep repeating the mantra of fusing because it really should be something we all do.

And I'll add that we should use the smallest fuse possible. My amps have 5 amp slow blow fuses on the high voltage rails, and it's never blown a fuse. Instead, I've had various components blow to protect the fuses when I've carelessly made connections with the amp turned on. Sadly, fuses don't protect our equipment from stupidity.

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  • 4 weeks later...
Guest shutupuface
Hi there;

One more comment.

I tried to contact, fuseone.com, for several months, a link that a member had suggested as being a good source of fuses.

They had, last time I went there, 3 email address's and I finally left all 3 the same email questions.

That was a total of at least 13 emails to that business, all went un-answered.

I just thought you might like to know my experience.

Another business came up recently, I will report back with my experiences with them at a later date.

Hi! I'm new to the forum. I apologize in advance for my ignorance. However, I recently aquired a pair of Large Advents. After reading the posts on this thread, I'm convinced that I need to fuse the speakers. But, I'm confused as to which fuses to buy. Also, after seeing the picutre of the AR's that are fused, I'm questioning my hookup for my speakers since the Advents have terminal posts with only a "0" above one terminal and "8 OHMS" above the other terminal. I am assuming that the "8 OHMS" terminal is the (+) side. However, I've only learned too well over the years what happens when one "assumes" much of anything. LOL Also, could you please educate me in the difference between "open" and "closed"

fuse holders. Thanks, in advance for the info! (and your forbearance) LOL

Best regards,

Rob

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Back again;

It appears that no-one here has blown a speaker driver or a fuse ever, judging by the overwhelming response to mine and Carl's question.

I will speaek no more about this subject.

I'll put my hand up here: I blew the fuses on my LSTs a few weeks ago. I apologize in advance if I repeat here what others have earlier read in my "LST Conundrum" thread.

I bought a pair of LSTs last summer; they needed refoaming, a number of new tweeters, a midrange and a capacitor or two, in addition to some TLC on the cabinets. Larry Lagace (vintage_ar) did the job for me, and did it beautifully. When I listened to the refurbished speakers at his shop, they sounded superb.

Got the monsters home and hooked them up to my receiver. With 400 wpc into a 4 ohm load I was pretty confident that it had adequate power and the ability to drive the difficult load that the LSTs present. The receiver has a cooling fan, which usually operates at a low (and nearly inaudible) speed. Within 10 minutes of listening to jazz at relatively low volume, the cooling fan went into "high speed" mode, which sounds like a New York subway train pulling into a station. Oddly enough, despite this the heat sinks were cool to the touch. Weird.

Shortly after this, the right channel died, then the left channel. Ugh. As it turns out, the fuses in the receiver (which I had retrofitted when I had it serviced) had blown. I replaced them, then noticed that the next problem was in the speakers: I could either have tweeter output (but no woofer output) or woofer output (but no tweeter output). Another member on this board very helpfully suggested checking the fuses...sure enough, they were both blown.

I replaced them (difficult to find the Buss FNM-2 fuses, as Vern has noted, and they can be pricey), and in doing so identified the fundamental problem that I believe was causing both the receiver and speaker fuses to blow: I have been using 12 gauge cable terminated in rather large spade lugs. The spades were too large, and were making connections that were never intended. I cut back the diameter of the wire at the binding post end, after discovering that AR had helpfully provided binding posts with holes in them into which a thin speaker cable fits. Problem solved. Now I can listen to what I want to, at the volume I want to, without worrying (too much) about either speakers or receiver.

This thread is key to understanding how to protect your speakers, and I would like to recognize and thank Vern for keeping it going. An ounce of prevention is certainly worth a pound of cure!

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I'll put my hand up here: I blew the fuses on my LSTs a few weeks ago. I apologize in advance if I repeat here what others have earlier read in my "LST Conundrum" thread.

I bought a pair of LSTs last summer; they needed refoaming, a number of new tweeters, a midrange and a capacitor or two, in addition to some TLC on the cabinets. Larry Lagace (vintage_ar) did the job for me, and did it beautifully. When I listened to the refurbished speakers at his shop, they sounded superb.

Got the monsters home and hooked them up to my receiver. With 400 wpc into a 4 ohm load I was pretty confident that it had adequate power and the ability to drive the difficult load that the LSTs present. The receiver has a cooling fan, which usually operates at a low (and nearly inaudible) speed. Within 10 minutes of listening to jazz at relatively low volume, the cooling fan went into "high speed" mode, which sounds like a New York subway train pulling into a station. Oddly enough, despite this the heat sinks were cool to the touch. Weird.

Shortly after this, the right channel died, then the left channel. Ugh. As it turns out, the fuses in the receiver (which I had retrofitted when I had it serviced) had blown. I replaced them, then noticed that the next problem was in the speakers: I could either have tweeter output (but no woofer output) or woofer output (but no tweeter output). Another member on this board very helpfully suggested checking the fuses...sure enough, they were both blown.

I replaced them (difficult to find the Buss FNM-2 fuses, as Vern has noted, and they can be pricey), and in doing so identified the fundamental problem that I believe was causing both the receiver and speaker fuses to blow: I have been using 12 gauge cable terminated in rather large spade lugs. The spades were too large, and were making connections that were never intended. I cut back the diameter of the wire at the binding post end, after discovering that AR had helpfully provided binding posts with holes in them into which a thin speaker cable fits. Problem solved. Now I can listen to what I want to, at the volume I want to, without worrying (too much) about either speakers or receiver.

This thread is key to understanding how to protect your speakers, and I would like to recognize and thank Vern for keeping it going. An ounce of prevention is certainly worth a pound of cure!

Hi there;

Your amp has thermal switches usually on the heatsink touching your output transistors.

There are to shut down the power, in each channel, if the transistors are overheated.

Often with a very difficult load, hot and neutral wires touching especially, the heat will shut these thermal switches off, actually it opens, before the heatsink can transfer the heat.

They are usually self-resetting also.

A number of amplifiers and receivers have speaker fuses accessible from the exterior of the cabinet rear.

The AR amplifier, for just one example, has 3 amps marked nearby.

This is really a fuse to protect the AR amp's output, not the speaker system.

AR did not go into any detail because they did not know which speaker system or brand you would end up with.

If one was to use the 3 amp fast blow glass fuse, with the AR amp, then at least only the AR-3A speaker system has some protection, as arrived at with the, Heath/AR AS-103/AS-103A/AR-3A speaker systems.

I would still suggest a slight de-rating at 3 amps even, considering the age of the drivers.

At this level I feel the slow blow 1 1/4 amp FNM fuses for those particular speakers is not needed now as much but twice as much protection is much better than none.

It does have a slight affect, with the damping factor, with the added resistance the amplifier sees.

If 3 amp slow blow glass fuses are used in the amplifier, rather than fast blow glass fuses, I am pretty certain that one can kiss one or more of the AR-3A drivers goodbye, if overloaded.

For the AR-LST's, at least, the 2 amp FNM slow blow fuses, while they are limited and still available at a very reasonable price $1.50 each, can provide a measure of protection.

If available, a slightly lower FNM fuse, presently at much greater cost, might be appropriate but 2 amp FNM is a lot better than a jumper across the LST's fuseholders, or cigarette foil across the fuse.

For the AR-LST's I would suggest that you use not larger than 4 amp fast blow fuses at this time, perhaps even 3 amp, barring further investigation of fast blow fuses.

By comparison the Dynaco A-25 uses 1 amp fast blow glass fuses.

There has been no FNM slow blow fuses recommended for the Dynaco classic speakers, only fast blow glass.

Nice to see that you are using heavy guage wire, along as it's stranded it is not too important to have a brand name mentioned here.

I have used moulded dual banana plugs which can accept that size wire, in fact 10 guage even.

They are less than $5.00 each, gold plated even.

The amp fan has a sef re-setting auto temperature switch that will, usually will allow the fan to run at slow speed and when it cuts in, closes, it is at the highest fan speed.

Check the fan, it sounds like the blades are rubbing for you to hear it so loudly.

Or the oilite or ball bearings are worn out.

I highly recommend the addition of chassis mounted fuse holders in the amp, as this is, depending on convenience, an easier location to access the fuseholders.

Your foresight of adding the fuseholders may have saved you many hundreds of dollars in amplifier repairs or even damage to a non-available part.

I'm back again.

I see that there is now over 2,000 viewers of this topic.

It obviously is of interest to a lot of members.

It would be really nice to see other members write their story of related information.

We all learn from others experiences.

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Hi! I'm new to the forum. I apologize in advance for my ignorance. However, I recently aquired a pair of Large Advents. After reading the posts on this thread, I'm convinced that I need to fuse the speakers. But, I'm confused as to which fuses to buy. Also, after seeing the picutre of the AR's that are fused, I'm questioning my hookup for my speakers since the Advents have terminal posts with only a "0" above one terminal and "8 OHMS" above the other terminal. I am assuming that the "8 OHMS" terminal is the (+) side. However, I've only learned too well over the years what happens when one "assumes" much of anything. LOL Also, could you please educate me in the difference between "open" and "closed"

fuse holders. Thanks, in advance for the info! (and your forbearance) LOL

Best regards,

Rob

Hi Rob;

Ignorance is accepted here, we are all less than knowledgeable when newbies.

There is no reason to apologize for asking a very valid and good question here.

There is specific Advent fusing information in the Advent library.

Advent library > other > service/schematics.

Advent recommended only the Buss Fusetron FNM 8/10 amp slow blow fuse, with an open clip style fuseholder.

This fuse and the fuseholder are rather expensive and are getting difficult to come across for the average person.

An open fuseholder and fast blow glass fuse is an alternative choice for you.

The Larger Advent has the same current capacity as the AR-2AX speaker system and others.

Refer to the AR library fusing information to see other speakers and the same fuse size.

A 1 1/4 - 1 1/2 amp fast blow glass fuse is about the perfect fuse size at this time, pending others doing fusing experimentation.

This fuse will blow faster than a slow blow, have spares on hand, about $.25 each.

Speakers marked + 8 or - 0 are polarity references only.

Normally when a 1 1/2 volt battery, no higher voltage, is attached with the + of the battery, to the speaker's + or 8 mark, the driver's, at least the woofer will move outward.

Other drivers are usually moving too short a distance to see that forward movement.

Some speaker systems high range drivers are wired out of phase as well.

With the capacitors in series with upper range drivers, a battery will not cause any forward movement to these, as it is filtered out, and only raw drivers will work.

Open and closed fuseholders, open, is a surface mounted open clip connectors style.

Chassis is closed, typical of the style used for amplifier fuses and are mounted into the chassis rear cabinet.

An open fuseholder allows easy and quick access to the fuses and allows air to cool the fuses.

This is usually shown fastened to the rear speaker cabinet but at the rear of the amplifier is also an alternative, keep it from shorting out though.

The chassis mount is only used in special applications, the Heath/AR AS-103/AS-103A speaker system, for one, used this method, with an o-ring, to add some extra cabinet seal.

This style does not allow any air to cool the fuse, so it is not as good a choice.

With the 0 and the 8, as long as you connect the cables to the amplifier using the same polarity, colour or ribbed wire to same screw, and at the speaker end, colour or ribbed wire to same 0 or 8 connector.

Vern

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  • 2 months later...
Hi there;

If you should even visit www.electronicsurplus.com, say hi to, Nancy and tell her where you found their website address.

I never asked for nor would I expect a discount at the price today of $1.50 U$ each.

At $1.50 U$ per 2 amp Bussmann FNM slow blow fuse, excellent customer service, communication and packaging, they deserve our support.

Hi again;

I am only updating the quantity left at 151 as of March 5/08.

They only have the 2 amp in the FNM fuse series in stock, at present, that we can use, they do have fast blow, etc,.

I have no vested interest in this company, I'm just a very satisfied customer of an item some of us can use that are at a very limited and attractive price.

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Those of us who have been around audio and/or electronics for any lenght of time understand the need for fusing, but I suspect this forum is frequented by a few newbies daily that never heard of the idea. Keep repeating the mantra of fusing because it really should be something we all do.

And I'll add that we should use the smallest fuse possible. My amps have 5 amp slow blow fuses on the high voltage rails, and it's never blown a fuse. Instead, I've had various components blow to protect the fuses when I've carelessly made connections with the amp turned on. Sadly, fuses don't protect our equipment from stupidity.

Hi Richard;

I was cruising the site and saw this older posting.

It say's that you have 5 amp slow blow fuses on the high voltage rails.

Is this correct?

Is this the manufacturers recommended size?

The reason I am asking is because, for examples, Dynaco and Leach both used fast blow glass fuses, not slow blow.

Can you check this out with the manufacturer?

These fuses are not protecting the speakers but are of interest to me.

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  • 2 weeks later...
Hi again;

I am only updating the quantity left at 151 as of March 5/08.

They only have the 2 amp in the FNM fuse series in stock, at present, that we can use, they do have fast blow fuses, etc,.

I have no vested interest in this company, I'm just a very satisfied customer of an item some of us can use that are at a very limited and attractive price.

Hi again;

Just to let you know that there is a 10% discount on web orders only for March.

Once again, I am only a very satisfied customer.

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Hi Richard;

I was cruising the site and saw this older posting.

It say's that you have 5 amp slow blow fuses on the high voltage rails.

Is this correct?

Is this the manufacturers recommended size?

The reason I am asking is because, for examples, Dynaco and Leach both used fast blow glass fuses, not slow blow.

Can you check this out with the manufacturer?

These fuses are not protecting the speakers but are of interest to me.

Dan,

I just saw your question and am now in the office. I'll check the schematic tonight, but off the top of my head, I believe the 5 amp fuses are fast blow. They are an absolute pain in the lower posterior to deal with due to their mounting location and are, without a doubt, intended to protect the amp rather than the speakers.

Heathkit included a "protection circuit" in the amp that monitors the amps output and is designed to open the output relay in a half cycle if the output exceeds design parameters such as excessive power (a dropped needle) or ultra low frequencies around 4 hz if memory serves me.

Saddly, I know for fact the circuit works........

Richard

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  • 4 months later...
Hi there;

You may wish to check out a surplus source for Bussmann FMN 2 amp fuses.

They are available at $1.50 US each and only in this one value, at this time.

Nancy is the contact person at Electronic Surplus, Inc, in Cleveland Ohio USA;

www.electronicsurplus.com.

Fast, very professional service, and very nicely packaged at a very attractive price while they last.

Also very businesslike.

They do answer their emails and are open for business.

Hi again;

In addition to the above mentioned business.

I've done done business with www.discountfuse.com recently, as well.

They are in business to sell many different value Bussmann FNM fuses and at a very reasonable price.

Excellent customer service and packaging, very businesslike.

I have no affiliation with either business.

Just passing on some information to the members on the limited and reasonable availablity of FNM Bussmann fuses of different amperages and others.

Vern

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I've done done business with www.discountfuse.com recently, as well.

They are in business to sell many different value Bussmann FNM fuses and at a very reasonable price.

Excellent customer service and packaging, very businesslike.

Hi Vern

Are you sure you intended to refer to www.discountfuse.com? They are more like a search site. There is a guy on ebay, who has an ebay shop called discountfuse, he has a lot of FNM fuses in different values.

BRgds Klaus

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Hi Vern

Are you sure you intended to refer to www.discountfuse.com? They are more like a search site. There is a guy on ebay, who has an ebay shop called discountfuse, he has a lot of FNM fuses in different values.

BRgds Klaus

Hi Klaus;

That is his or their website address.

I found this business from an eBay auction I was bidding on and won.

From what I read this man has several decades of fuse experience.

Vern

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  • 1 month later...
Guest atbglenn

Hello all, I'm new here. Although my speakers aren't considered classic. They are Monitor Audio 700 Gold MKII. Since they haven't been made in years, and parts are no longer available, I decided to fuse the tweeter. I'm using a fast blow 1/4 amp fuse as shown below. BTW, I'm no stranger to real classic audio. I've owned AR 2ax, AR4x, Large Advents, and others :) Another reason why I'm fusing them, I now use these on my computer driven with a Parasound Pre amp and power amp.

DSC_1660.jpg

DSC_1692.jpg

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Hello all, I'm new here. Although my speakers aren't considered classic. They are Monitor Audio 700 Gold MKII. Since they haven't been made in years, and parts are no longer available, I decided to fuse the tweeter. I'm using a fast blow 1/4 amp fuse as shown below. BTW, I'm no stranger to real classic audio. I've owned AR 2ax, AR4x, Large Advents, and others :) Another reason why I'm fusing them, I now use these on my computer driven with a Parasound Pre amp and power amp.

Hi there;

I am not familiar with these speakers and their power ratings.

Was a jumper removed to add the tweeter fusing?

The woofer is likely not available as well?

Why not place the fuse in series with the complete speaker, perhaps upwards of 1/2 - 1 amp fast blow?

Vern

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Guest atbglenn
Hi there;

I am not familiar with these speakers and their power ratings.

Was a jumper removed to add the tweeter fusing?

The woofer is likely not available as well?

Why not place the fuse in series with the complete speaker, perhaps upwards of 1/2 - 1 amp fast blow?

Vern

Hi there Vern,

The woofers are no longer made as well. I did remove the jumper and put a 1/4 amp fuse in it's place to protect the tweeters from defective mp3's, etc that sometimes cause momentary high pitched squeals. So far I've been lucky, and I haven't experienced any recently. The speaker's power rating is 100 watts program (I think) My amp is 125 watts rms per channel. And since the speakers are set up in a near field situation, I'm not playing them anywhere near their maximum power rating.

I think I'll take your advice though, and fuse the whole system. It's better to be safe than sorry. But I'm still going to keep the tweeter fused separately with the 1/4 amp fuse. So you think a 1 amp fast blow will do the trick?

Glenn

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Hi there Vern,

The woofers are no longer made as well. I did remove the jumper and put a 1/4 amp fuse in it's place to protect the tweeters from defective mp3's, etc that sometimes cause momentary high pitched squeals. So far I've been lucky, and I haven't experienced any recently. The speaker's power rating is 100 watts program (I think) My amp is 125 watts rms per channel. And since the speakers are set up in a near field situation, I'm not playing them anywhere near their maximum power rating.

I think I'll take your advice though, and fuse the whole system. It's better to be safe than sorry. But I'm still going to keep the tweeter fused separately with the 1/4 amp fuse. So you think a 1 amp fast blow will do the trick?

Glenn

Hi Glenn;

For the inline fuse for the entire speaker, without knowing the particular specs, you can start at 1/2 amp fast blow if you wish.

There is still a healthy amount of power going to the speakers.

You just do not want to go too high and then oops. LOL LOL

The fuses are only around $.25 each so you should have a few spares onhand, perhaps in their retail container taped to the rear of the speakers.

What is the diameter of the woofer approximately?

Good luck.

Vern

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Guest atbglenn
Hi Glenn;

For the inline fuse for the entire speaker, without knowing the particular specs, you can start at 1/2 amp fast blow if you wish.

There is still a healthy amount of power going to the speakers.

You just do not want to go too high and then oops. LOL LOL

The fuses are only around $.25 each so you should have a few spares onhand, perhaps in their retail container taped to the rear of the speakers.

What is the diameter of the woofer approximately?

Good luck.

Vern

Vern,

The specs are : Rear ported 6 1/2" cast frame, polypropylene woofer, 1" metal alloy dome tweeter, recommended power is 20 to 100 watts, 8 ohms, sensitivity 89db.

I have several boxes of fuses in stock from 1/4 amp on up from there. I have a local old time electronics distributor near by just in case. :)

BTW, I've built a few DynaKits in my day. Starting off with a Stereo 70 power amp and PAS3x Preamp in 1969. Also built a MKIII 60 watt monoblock that I used as a Bass amp coupled with a Pam1 preamp someone gave me, and a 15" JBL D130. I also owned a pair of A25's that I bought around 1973. Great stuff! I wish I still had them.

Glenn

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Vern,

The specs are : Rear ported 6 1/2" cast frame, polypropylene woofer, 1" metal alloy dome tweeter, recommended power is 20 to 100 watts, 8 ohms, sensitivity 89db.

I have several boxes of fuses in stock from 1/4 amp on up from there. I have a local old time electronics distributor near by just in case. :)

BTW, I've built a few DynaKits in my day. Starting off with a Stereo 70 power amp and PAS3x Preamp in 1969. Also built a MKIII 60 watt monoblock that I used as a Bass amp coupled with a Pam1 preamp someone gave me, and a 15" JBL D130. I also owned a pair of A25's that I bought around 1973. Great stuff! I wish I still had them.

Glenn

Hi Glenn;

With the small bass reflex woofer I would stay around 1/2 +/- amp fast blow total inline fuse size.

Generally the bass reflex systems are not as power hungry nor have as much power handling capabilities.

Vern

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