replacing/renewing old crossover capacitors.

Discussion in 'DIY Discussion' started by rob, Oct 20, 2004.

  1. rob

    rob SCHMOOOOKIN

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    ive got some celestion ditton 15's (eventually found a nice , unbutchered pair) and ive been thinking about renewing the components on the crossovers , especially the caps as ive found out the older ones are prone to drying up.
    because of the speakers age i dont think this would do any harm. i have no idea as to the condition of the old ones as i have never listened to a pair of brand new dittons however i do think they may be a bit "tired".
    ive had a look through the wilmslow audio catalouge and they recon their hoveland musicaps are the best there is.
    so , should i go with them or do you guys have any recommendations for some good quality replacments?
    i have no idea of the values of the old caps because i have yet to take a look at them.
    any advice would be great.
    thanks,

    Rob.
     
    rob, Oct 20, 2004
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  2. rob

    Graham C

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    Only capacitors with something like '+' or '-' or 'non-polar' dry up. These are distant cousins of batteries and have chemicals that age. Capacitors that are definitely solid plastic are only damaged by over-voltage [unlikely in a speaker - other things would die first] and should last. Usually you need to replace with the same type.

    Ask Falcon for cheaper advice
     
    Graham C, Oct 20, 2004
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  3. rob

    rob SCHMOOOOKIN

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    ive got the old caps from the other pair of dittons and they look like batteries.
    thers no polarity markings on them.they are made from red tin with a silver metal top and a black rubbery plastic bottom.
    thers no pcb whatsoever just one cap with two big wire coils that are bolted to a metal rod.
    the cap says "c.c.l. (presumably the make,from glasgow i think) then it says , 24 uf then it says 25 vdc rev , then we99/ras b7.

    it looks like an old battery because of the shape and there is a contact stub on the top , like on the top of a battery.
    the crossover does look to be pretty basic.

    i would imagine these to be in my new dittons although im not going to use them as a rule , so what do you think?


    cheers,


    Rob.
     
    rob, Oct 20, 2004
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  4. rob

    Graham C

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    You are spot on with your diagnosis

    24uF = the capacitance, needs to be the same

    25vdc = [...obviously!] 25 volts DC maximum..no reason to be stingy, something higher than 25V will last longer and work better

    rev = reversible = non polar = bipolar. Sometimes they put 2 pluses or 2 minuses. That would also mean reversible.

    They are actually made of 2 caps connected in series inside. Each has a '+' and a '-'. They are connected either in the order +--+ or -++- internally, so you only see the end connections. The reverse connection is supposed to make them able to withstand AC signals, but they gradually breakdown over many years. The other plastic type are always OK reversible.

    From Falcon:

    http://www.falcon-acoustics.co.uk/pl28p7.htm

    Alcap 100v 25uF = 116p, 50v = 62p

    If you tell them you need 24uF, they will test it, and send you that value probably, for maybe slightly more. They are helpfull like that.

    As with everything in audio, there is no upper limit on what you could spend....
     
    Graham C, Oct 20, 2004
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  5. rob

    rob SCHMOOOOKIN

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    thanks graham. :beer:
     
    rob, Oct 20, 2004
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  6. rob

    GTM Resistance IS Futile !

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    Get yourself some Polypropolene caps. Don't need to pay over the odds for "audiophile" grade ones on such old speakers. Any Poly prop will be leagues ahead of a electrolytic in s/q terms anyway. Having said that Maplins do very good value "audio" grade polyprops on their website. Just make sure you get the same value and any voltage that is higher than the current one, (polyprops are very often rated at 250v + so you shouldn't have any problems there)

    http://www.maplin.co.uk/Module.aspx?ModuleNo=393&TabID=1&source=15&WorldID=3&doy=25m10


    GTM
     
    GTM, Oct 25, 2004
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