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Is It A Bulb Or A Fuse?


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Good afternoon

 

 

Can i ask for some help please, using my JBL EON 1500's last night, as i was settin up my gig for tonight. THe people i am working with tonight asked if they could go through my mixer with their Radio Mics. IN i plugged it etc, they switched them on and the loudest whistle i have ever heard and you guessed it, it has taken the horn out of action. Tried some on the job repairs, tokk out about 14 screws and it reveals the inside and their are 2 what i can describe as glass fuses but they could be bulbs and the 1 as definatly blown. Been onto JBl's site this morning and they state that the speakers are fitted with bulbs but as i say they lok like fuses to me.

Been to Maplins who have looked at me like i am mad and they have asked to see them - the next part they appear to be soldered onto the board and not just push in which leads me into total confusion/

 

SoO as always any help/advice would be very much appreciated.

 

Cheers

 

Chris

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I have some carbulbs in mine and they ar soldered to nthe curcuit board They are leach cabs but are a copy of an old JBL design I just use them for side fill now when using the big pa they must be 20 years old but still got a crisp clean topend .so they could be car bulbs just check the values on them Halfords have a good range in stock

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http://jblproservice.com might be a helpful website too - seem to have a wealth of info on their speakers and even diagrams of the crossover networks , etc.

 

EDIT: http://jblproservice.com/pdf/EON%20Series/...0%20Network.pdf lists the bulbs as Sylvannia SK-3 CWTLDS - which i don't think is correct (Google says 0 results). I thought all bulbs would have some sort of etchings on them...

 

 

David

Edited by gadget

DJ David Graham

Tel: 01204 537716 / 01942 418415

Email: hello@djgraham.co.uk

FB: http://facebook.com/djdavidgraham

Web: [under construction - it really is coming soon :)]

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For the most part they are inserted to offer a degree of limiting, since the filament heats up as the tweeters are overloaded, and as they get hotter the resistance increases. As you can guess, the correct specs are vital to the correct operation of your speaker. If the specs are wrong it will either offer no protection at all (meaning the next time a mic is dropped, it'll be your voicecoils that pop) or else they will limit too soon and either blow due to overvoltage or simply cramp the operation of the tweeters.

 

Some of the Peavey crossovers for example use 24V rated lamps..bear in mind an amp can give out + / - 160V DC or more during fault conditions.

 

 

.

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The Sylvannia SK3 is 12.8 Volts @ 2.1 Amps

 

Jim

 

 

Awesome... Dj-U has probably solved the problem before JBL will have received/ read their email... The only think SK-3 brings up in the UK is Stockport Cheshire.. A USA supplier has them for about 70 cents. so cheap as chips - but i'll bet their P&P might be ridiculous!

 

I can see why they might be interpreted as wired fuses though - due to the long leads on them.... Wired in series that's about 24 volts, same as the Peavey bulbs.

 

David

DJ David Graham

Tel: 01204 537716 / 01942 418415

Email: hello@djgraham.co.uk

FB: http://facebook.com/djdavidgraham

Web: [under construction - it really is coming soon :)]

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Still no joy unfortunately, the Electrical Engineers at work are working on them now, they even contacted JBL direct who were not helpful- even promised to contact us when they knew but did not hold my breath. Contacted Harmann last Tuesday and they emailed back this aftenoon recommending another company so i am in the dark still but i am leaving it uto our Medical Engineers at work who repair all the Hospital equipment, mind they are all qualified sound techs too.

 

Thanks to all who have offered help.

 

Chris

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Good afternoon

Can i ask for some help please, using my JBL EON 1500's last night, as i was settin up my gig for tonight. THe people i am working with tonight asked if they could go through my mixer with their Radio Mics. IN i plugged it etc, they switched them on and the loudest whistle i have ever heard and you guessed it, it has taken the horn out of action. Tried some on the job repairs, tokk out about 14 screws and it reveals the inside and their are 2 what i can describe as glass fuses but they could be bulbs and the 1 as definatly blown. Been onto JBl's site this morning and they state that the speakers are fitted with bulbs but as i say they lok like fuses to me.

Been to Maplins who have looked at me like i am mad and they have asked to see them - the next part they appear to be soldered onto the board and not just push in which leads me into total confusion/

 

SoO as always any help/advice would be very much appreciated.

 

Cheers

 

Chris

 

Im pretty sure they festoons that are used as close circuit protection, god knows why when a fuse would do the same job.

 

like i say i carnt remember exactly what the protection method is, but if its not festoons it'll be fuses or fusable links! whichever the case may be, if they are blown, it might be a good idea to0 have it repaired by an engineer rather than doing it yourself as a decent engineer will check the rest of the board to make sure nothing else has blow as a knock on effect - you could end up replacing the protectiove device time and time again and every time power is put through, it may blow again and again!

 

usually its just the 'fuse' that goes, however i have known other parts go as a result over the fuse going! this is mainly because all circuit boards now a days are made to a price and with cheap components - even in the 'high end' gear!!!

 

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Im pretty sure they festoons that are used as close circuit protection, god knows why when a fuse would do the same job.

 

I refer you to my previous post.

 

They are not fuses, they are lamps which have a completely different function than to blow on an overload. They are designed to heat up if the tweeters are overdriven, this raises their series resistance and lowers the current through the tweeter. It is a form of limiter.

 

If the lamps have blown, the speakers have been overdriven and then some more till they've glowed so bright they've popped.

 

They act as a sort of thermistor. Similar devices were built into the GPO 706 table telephone of the late 1950's to compensate for subscribers who lived very close to the exchange and suffered over-loud reception.

 

 

.

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