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Old 14th August 2012, 11:24 AM   #1
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Default Cross over help - low tweeter volume.

Hi all, first post here.

Today I picked up a pair of TDL Nucleus 3 floorstanders for a pretty good price. However, I've got them home and I think there's a problem with one of the cross overs. Please bear with me here, I am a complete noob when it comes to the internals of speakers. But I'm interested in building a few skills/knowledge.

Basically, one tweeter was much lower volume than the other. I swapped it over to the other speaker/cross over, and it sounded fine. So my conclusion is that there is a problem with the cross over.

Can anyone suggest a starting point or procedure for figuring out what the problem may be? I've attached a photo of the offending item. High frequency on top.

Very limited electronics knowledge here, so take it easy on me!
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Old 14th August 2012, 11:53 AM   #2
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Check the wiring with an Ohm meter and if all that is fine, change the blue bits. They are bipolar capacitors and degrade over time.
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Old 14th August 2012, 12:04 PM   #3
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+1 the electrolytics may have dried out, giving a much higher resistance path through the capacitor.
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Old 14th August 2012, 12:31 PM   #4
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Thanks for the advice guys. Will pick up a multimeter tomorrow and see what I can find.
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Old 15th August 2012, 10:34 AM   #5
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Does anyone have any tips for extracting the capacitor from the glue that has been used to fix it to the panel? It's hard to see from the photo, but the cap and resistor have basically been half submerged in what looks like hot glue gun glue.

Maybe it would be easier to place the new cap somewhere else, and just wire to and from it? Will still be tricky to get to the resistor through the glue.
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Old 15th August 2012, 11:39 AM   #6
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if its hot melt glue, then you should be able to simply prise the glue from the terminal plate with the right tool. Knife, flat screwdriver, chisel?
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Old 15th August 2012, 02:16 PM   #7
system7 is offline system7  United Kingdom
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Electrolytics are designed to be stable to 85C, and everything evidently survived the hot glue application.

I dunked my crossovers in hot water around 60C and the hot glue came away easily if messily enough. I then dried everything carefully. Most components and circuit boards get a final wash in water as part of manufacturing, so I wasn't too worried about getting them wet.

Click the image to open in full size.
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Old 15th August 2012, 04:07 PM   #8
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Quote:
Originally Posted by Han120i View Post
Maybe it would be easier to place the new cap somewhere else, and just wire to and from it?
That's what I would do. Good luck. It may take a bit of work but you should be happy once complete.
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Old 15th August 2012, 09:34 PM   #9
sreten is offline sreten  United Kingdom
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Hi,

FWIW the simplest procedure is to replace all the bipolar electrolytics
in both crossovers with new ones, possibly upgrading the treble
series capacitors to metallised film polypropylene.

Don't just fix the duff capacitor.
Heat gun on hot glued stuff works.
(Hair dryer with restricted airflow).

rgds, sreten.
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Last edited by sreten; 15th August 2012 at 09:42 PM.
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Old 15th August 2012, 09:35 PM   #10
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Thanks for the advice everyone. Another suggestion I had was using a hair dryer to loosen up the glue around the cap. Maybe this might be a way to get at the submerged leads? Any thoughts?

Also another question - the capacitor is labelled 6MF. I assume this means 6 micro-farads, as opposed to milli-farads which the "M" suggests? Is this a standard size? I'm struggling to find a replacement in the online stores. All seem to be 5.6 uF or 6.8 uF.
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