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Should I recap the crossover in a 1975 loudspeaker?

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Should I recap the crossover in a 1975 loudspeaker?

Postby TheColin » Sat Aug 04, 2018 6:52 pm

Hi,

I just picked up a pair of 1975 Telefunken L7000 loudspeakers which I intend to use in my living room. However, I discovered that the woofer on one wasn't working and I traced this to a faulty capacitor in the crossover. So I will replace this capacitor in both speakers to get the pair working, but then I got to thinking perhaps I should just replace all the caps in the crossovers? They'll have all been there since 1975 and so perhaps they are about to go too, or perhaps they are 'leaky' (I'm an electronics noob btw so I'm learning as I'm going here), so maybe the speakers will sound even better with a new set of caps?

So the questions are: should I recap the whole thing - and if so why? Are there other components I should switch out now too?

Cheers,
Colin
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Re: Should I recap the crossover in a 1975 loudspeaker?

Postby James Perrett » Sat Aug 04, 2018 8:36 pm

It depends on the type of capacitor used. Film capacitors will usually be OK but electrolytic capacitors may have dried out and changed their value. Could you post a photo of the crossover?

Edited to add: Having found the circuit diagram on the Radiomuseum.org website it looks like C801, C802, C804 and C805 are all non polar electrolytics while C803 is a film capacitor. I would guess that it was C801 that failed short circuit in the speaker that stopped working. One source of suitable capacitors would be

https://www.falconacoustics.co.uk/alcap ... ?limit=all

(though I've not bought from them personally)
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Re: Should I recap the crossover in a 1975 loudspeaker?

Postby resistorman » Sun Aug 05, 2018 4:05 am

I think it's a good idea to replace electrolytic caps that old. I've had my knee replaced and I'm not that much more aged!
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Re: Should I recap the crossover in a 1975 loudspeaker?

Postby ef37a » Sun Aug 05, 2018 7:55 am

First of all, the only way a CAPACITOR could cause a woofer to cease working is if it went short circuit in a conventional cross over network. You are lucky the amplifier survived!

If one cap' has failed it is likely the others will do so but do not be tempted to replace the non-polar electrolytics with modern foil types even though the latter are now much smaller than in 1975! Foils are much more "efficient" than electros and will screw up the frequency response.

Dave.
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