Kef 105/3 crossover - diyAudio
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Old 6th January 2010, 09:22 AM   #1
sbx is offline sbx  England
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Default Kef 105/3 crossover

Hello I have a pair of these speakers and have been reading about people replacing the capacitors due to ageing. I have had a quick look inside my cabinets and the caps look fine i.e not swollen, but I have read that they dry out. If it is advisable to replace them, what caps would any one recommend? I have a schematic of the crossovers and there a total of 23 caps per speaker The values on my schematic are as follows;(value times total)
240 x 2
100 x 7
80 x 4
60 x 1
50 x 3
20 x 3
15 x 1
7 x 2

Any advise would be greatly appreciated, I think these are fantastic speakers and about 18 months ago all the bass units were re-foamed complete with new centre doughnuts so they should be okay for the future...I hope. I know Kef do not have any more drivers for this model now, that is why I am asking if it would be worth all this extra work and would I notice any improvement? thinking along the lines if it ain't broke etc...

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Old 12th February 2010, 10:49 AM   #2
Toolman is offline Toolman  Canada
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Default Kef 105/3 crossover

Hello sbx, I have just joined the diyaudio group so forgive me if I am over stepping boundaries. I too have just acquired a set of 105/3's and I have just had the bass units re-coned. My problem is that it appears I am missing the highs from one side. I swapped the speaker wires to eliminate the source and then opened up the cabinet. No swollen capacitors or apparent open circuits but one of the capacitors has lost its plastic identification cover. On closer examination the capacitor was leaning (incontact) with what looks like a ceramic block resistor. Between them was some of what was left of the capacitor cover (somewhat melted and discoloured). All this to ask where can I get a copy of the schematic for the board and does anyone have a simple test to check the function of the board and I'm assuming the tweeter?

Toolman
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Old 12th February 2010, 11:55 AM   #3
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sbx,

as there are so many capacitors, and a lot are high capacitance values, it is going to be expensive to replace them all with new high quality,
long life capacitors.

I you are able to Post the Schematic of the crossover, I will advise you which ones are the most critical to spend money on,
and which ones will be OK to replace with lower price caps.
Either the KEF printed schematic, or your own hand-drawn, will be OK,
but do show which cap values are where, and show all inductors' and resistors' positions, and the connection points for the drivers.

************************************************** ***************

Toolman,

I'll comment more on yours after we see what sbx can Post here,
though you can look in the other 105/3 at its crossover to see what is printed on the equivalent position cap there
-the one which corresponds to the burnt cap in the missing highs' 105/3 - and Post that information here.
The melted cap has likely gone Open-Circuit and is no longer passing signal.
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Last edited by alan-1-b; 12th February 2010 at 11:59 AM.
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Old 12th February 2010, 01:09 PM   #4
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Hi all,
Maybe this is of any help
Kef 105.3 assembling
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Old 13th February 2010, 12:53 PM   #5
Toolman is offline Toolman  Canada
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Alan, and Inductor, thank you for the information. I have done a bit of testing and determined that the tweeter isn't working. (applied signal directly and no output). I then applied signal to the HF board and there is output. The cpa may not be toast but I will replace it any way as it has been exposed to excessive heat anyway. I include a photo of the board in question.
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Old 14th February 2010, 01:26 AM   #6
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Toolman, when using components (new) for repairs, always make it with a new matching pair and repair the other speaker too for a perfect match in sound output. Unless it's the same exact component/tolerance. (As someone said before, there are exceptions, like a pair of speakers fine-tunned different from each other to achieve for the same result/sound footprint).

Last edited by Inductor; 14th February 2010 at 01:31 AM.
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Old 14th February 2010, 12:51 PM   #7
Toolman is offline Toolman  Canada
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Default KEF 105/3 crossover

Inductor, good point ref the balance of new components. I note as well that the schematic you directed me to shows the capacitor in question to be 15 mfd, the one on my board (and confirmed on the other cabinet) is a 16 mfd.
As I have eliminated the board as the source of no output I now have to figure out how to separate the tweeter from the woofer without causing further damage. There is a nut in the top but when I turn it so too does the whole tweeter. Any thoughts.
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Old 20th February 2010, 05:53 PM   #8
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Toolman,

my uniQ drivers are later models than those in the 105/3,
however they also have a screw on the back.
I haven't turned it because the drivers are working well,
though I think it is possible the inner tweeter section unscrews.
Safest is to send the entire driver to the authorized KEF service centre in your country ...
{and not simply to a KEF selling shop's technician - beware, some ruin complicated components}.
Look under:- KEF Global for service details, or email to them.

I'll Post more about that crossover when I have time available - hopefully soon.
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Old 20th February 2010, 06:02 PM   #9
sbx is offline sbx  England
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Quote:
Originally Posted by alan-1-b View Post
Toolman,

my uniQ drivers are later models than those in the 105/3,
however they also have a screw on the back.
I haven't turned it because the drivers are working well,
though I think it is possible the inner tweeter section unscrews.
Safest is to send the entire driver to the authorized KEF service centre in your country ...
{and not simply to a KEF selling shop's technician - beware, some ruin complicated components}.
Look under:- KEF Global for service details, or email to them.

I'll Post more about that crossover when I have time available - hopefully soon.
Hi Alan, I have bought some of the later 4th generation UniQ from Kef purely as back up for the future, I know what you mean about the slightly different fitting, a friend of mine replaced his last year and came across this issue, which he has successfully worked around

Cheers for the reply(I am in the UK BTW and dealt direct with Kef support who offer a very good service)

All the best
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Old 20th February 2010, 06:11 PM   #10
sbx is offline sbx  England
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Sorry guys I have just realized I have missed about half a dozen posts on here, for some reason the last one was the only one forwarded to me
Hope this diagram will be of great use to you

Cheers
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