Any electonic experts here?

  LastChip 16:01 26 May 08

Here's the story.

I have a pair of high end hi-fi speakers that are 30+ years old; and I love 'em.

Sadly, one's ceased to function. Each speaker has four drivers, supplied via a crossover network.

As the whole speaker ceased to function, logic told me it was probably the crossover that was to blame; this being common to all four drivers, but on checking, the main "woofer" had failed. Surprisingly, this isn't a problem, as I've managed to source a pair (guaranteed working) via ebay. However, it crossed my mind that maybe the crossover had contributed to the failure, or, maybe the speaker failure screwed up the crossover - why else would all drivers fail to work? Note: all the other three drivers have been checked individually and are OK.

Anyway, on de-soldering one end of each capacitor, it does indeed seem as though one has gone down (please note, I only have very basic electronic knowledge). The capacitor is rated at 60uf at 50v. It seems the nearest modern equivalent is 47uf, paralleled with a 10uf giving 57uf total.

So my question is, is this likely to be critical in the network or should I (maybe) add a further 3.3uf to take the nominal total to 60.3uf and how if anything, is it likely to affect the sound balance of the pair of speakers?

Further, I have no way of either testing (or knowing) the value of the inductors in the network, other than to check for continuity. (I know from Internet research, these were hand wound by the manufacturer - who no longer exists) Are these likely to have failed?

  octal 16:45 26 May 08

It's very unlikely the inductors have failed and it's unlikely a speaker failure would cause the crossover to be damaged as a result as it is a passive device. I think the value of 57uF is close enough. My main concern is the capacitors are probably non-polarised type, so ordinary electrolytic caps would not work, it would be best to use Mylar capacitors.

  octal 16:48 26 May 08

In fact Cricklewood Electronics sell the very ones you need click here

  LastChip 17:11 26 May 08

The page you've pointed me to, indicates they are Polypropylene Capacitors ANSAR SUPERSOUND Axial.

Are these non-polarised? If so, it's the perfect match - thanks.

Once I know for sure, I'll order it.

  octal 17:17 26 May 08

Yes Polypropylene are non-polarised and I think these are the very ones that are used in crossover networks.

  octal 17:19 26 May 08

Just one point, they are large so take note of the dimensions.

  LastChip 17:27 26 May 08

Thanks octal - you're a star!

Yes, I did note the dimensions, but being old, everything on this board is built like the proverbial brick built ... so space is not an issue.

Thanks again - ordering now.

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