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Questions on Large Advent fuse


gremlin

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Hi,

This is my first post.

I have both Large and Smaller Advent. The SA is refoamed and the LA is the next one in line. Anyway, I was going through the library of this website and checked the Advent section. I saw there is a document about adding fuses to the LA. Now I have two questions:

1/ the document specifies FNM 8/10. I've found the spec from the internet

FNM-8/10 Product Details & Specifications

Item Name: FNM-8/10

Manufacturer: Bussmann

Packaged Weight: 2 lbs

Characteristic: Time delay

Votage Rating: 250 ac

Current Rating: 0.8 amp

Description:

TIME DELAY CHARACTERISTICS

250 VAC

8/10 AMPERE

INTERRUPTING RATING 35 AMPERE AT 250 VAC, 10000 AMPERE AT 125 VAC

FERRULE TERMINAL

DIAMETER 13/32 INCH

LENGTH 1-1/2 INCH

APPROVAL UL 248-14, CSA, CE

FUSETRON[R] BRAND

FNM MODEL

Does it have to be FNM style or package? Or can I just use any 0.8A 250VAC time delay fuse? I cannot find this FNM 8/10 fuse in Home Depot.

2/ Should I use them on both LA and SA?

Thanks for any reply.

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I've installed fuse holders in a number of speakers. They are the type where you insert the fuse and push it in with a push cap the is twisted to lock the fuse in place. What I use are AGC 3 types - fast blow. in the 1.5 to 2 amp range. Usually start the customer out with a lower rated fuse and tell them if it's failing much too soon, then gradually ramp up the amperage until just at the point where it doesn't fail easily.

They have been installed in Spica TC-50's as part of the terminal cup.

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Hi,

This is my first post.

I have both Large and Smaller Advent. The SA is refoamed and the LA is the next one in line. Anyway, I was going through the library of this website and checked the Advent section. I saw there is a document about adding fuses to the LA. Now I have two questions:

1/ the document specifies FNM 8/10. I've found the spec from the internet

FNM-8/10 Product Details & Specifications

Item Name: FNM-8/10

Manufacturer: Bussmann

Packaged Weight: 2 lbs

Characteristic: Time delay

Votage Rating: 250 ac

Current Rating: 0.8 amp

Description:

TIME DELAY CHARACTERISTICS

250 VAC

8/10 AMPERE

INTERRUPTING RATING 35 AMPERE AT 250 VAC, 10000 AMPERE AT 125 VAC

FERRULE TERMINAL

DIAMETER 13/32 INCH

LENGTH 1-1/2 INCH

APPROVAL UL 248-14, CSA, CE

FUSETRON[R] BRAND

FNM MODEL

Does it have to be FNM style or package?

Or can I just use any 0.8A 250VAC time delay fuse?

You can not just use any type of fuse for speaker protection.

I cannot find this FNM 8/10 fuse in Home Depot.

2/ Should I use them on both LA and SA?

Thanks for any reply.

Hi there

In comparing fast blow and slow blow fuses I will be using AR fusing information, from the AR library, with the FNM/FLM Buss/Littlefuse slow blow fuses.

AR-3A's used an FNM/FLM 1 1/4 amp fuse.

Much has been published as to the output capabilities of the venerable AR-3A's.

Heathkit AS-103/A kits, using AR-3A componenets, used fast blow 3 amp fuses in a chassis mount holder.

AR never suggested fast blow and Heath never mentioned slow blow so we can only try to convert, always downwards of course for added driver safety.

Heath's chassis mounted holder was not a very good idea as the heat is contained inside, better than none though, rather than an open holder style version.

The 8/10 FNM/FLM fuse is used by AR-3, AR-5 and AR-1X for just 3 models, allowing a substantial amount of power before blowing.

Checking out the AR fusing sheets in the library will give you an idea of their wattage capacity.

I would suggest not using over 1 1/2 amp fast blow fuses, more likely 1 1/4 amp rating.

Keep spares onhand.

An AR-5 with the suggested FNM/FLM 8/10 fuse will give more than enough output and protect the drivers under most instances.

Dynaco A-25's used 1 amp fast blow and they have a tremendous output as well.

Both Advents will use the same size fuse.

The very expensive FNM/FLM fuses are generally only at surplus suppliers and their open fuse clip is very difficult, if not impossible, to locate.

I have seen chassis mount fuseholders for them but they are big, expensive and may not fit in the crowded area around the terminals.

To keep with the classic speaker recommendation is great but a FNM fuse and open fuseholder could easily cost $20.00 per pair.

Fast blow fuses (5) and 2 open style fuseholders may cost $5.00.

My thought on their location is at the amplifier end so that there is no chance of wires shorting under carpeting, furniture and also shorting at the speaker terminals.

There is a few amplifiers that already have chassis fuseholders factory installed, this lessens the need for additional fuseholders or chance of amplifier damage as well.

The tab tends to break off very easily on the square Littlefuse holder.

I suggest an alternate style, chassis mount with round head, either screw-in or push and turn type.

The square Littlefuse fuseholder will be destroyed if you insert the cap without a fuse in the body.

Caps in red and white colour are generally available on ebuy, I haven't seen the Littlefuse OEM black ones for a long time.

There is a look-a-like square one being sold on ebuy, I know nothing about them.

Just my thought for today.

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