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Old 29th September 2009, 08:00 PM   #1
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Default Celestion ditton 44's - capacitor GONE!! Help!!

I bought some 44's, loved them for an evening, went to replace the silly speaker terminals in the morning, and found a chanel had gone. A very faint and distorted sound is all thats coming through. I've tested the speaker cones and they are all fine, the signal from the amp is good also. My only guess is that, as they were left unused for some time, that a capacitor has gone. I would love to replace them all anyway, but I am no tec' head, and I am on a tight budget.

I desperately need some advice about what sort/make of capacitor I can look to replace the old ones with. There are some replacement crossovers on e-bay, but I think it might be unwise to replace the boards with another set of old caps.

Could I take the capacitor specs to RS, and just replace them directly with modern units, not designed with the audiophile in mind?

Would be most grateful for any help - have no hi-fi - going mental.
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Old 29th September 2009, 08:50 PM   #2
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Make sure that you get non-polarised caps (sometimes called bipolar) and match the capacitance and working voltage.

What are the markings on the old cap?

BTW, how did you test the speaker cones?

edit: it may be prudent to test the caps. If the cap has indeed gone high impedance then you should be able to measure a higher AC voltage across it compared to the good speaker when playing music. Do you have a meter? I've spent too much money doing the "trial-and-error" fault finding technique.
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Old 29th September 2009, 10:22 PM   #3
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I helped Lorien replace his binding posts last night, so I've seen inside the speakers, and I did test the board a bit by bypassing caps with a wire, but couldn't isolate the offending item.

We tested the speakers by wiring each one in turn to the direct signal at a fairly low volume. All of the drivers are sound.

At 30 odd years old it seems prudent to me to replace all of the caps, even if for the pocket's sake it need be with the non-exotic types. I think that standard modern electrolytics, for example, should blow these old ones away, right?

I have a meter. To test a cap, do I place the terminals across the cap? Will AC voltage be consistent, or vary with music? I ask because whenever I've tried to multimeter music signals, my reading jumps around like it's gone mad. I don't really know how to use it properly.

Lucas
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Old 29th September 2009, 10:35 PM   #4
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I tested the speakers individually bu introducing direct feed from the amp at low volume. All responded. Secondly I ran the positive from the primary conection point on the cross over, then traced backwards from the primary negative connection. This produced a selection of music at different frequencies from individual cones/tweeter. Common sense seemed to indicate that the first cap had gone, but I couldn't make sense of wyh that only produced sound from one speaker when I took it out of the loop.

My gut tells me to replace the lot so this is not an experience I have to repeat. I've bought a rogers cadet 3 to play them on, and I'm hoping for a long stretch of trouble free pleasure with the set up. I am a little concerned that simple, non audio, though properly rated caps will return less sound quality than the tired old ones. Do you think this is the case - or will modern replacements do the job well.

Many thanks - LB
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Old 29th September 2009, 11:51 PM   #5
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It's very likely that a 20yr old cap has dried up and gone high impedance and yes, modern electrolytics are much better (must be non-polarized of course.) But what's the evidence of that here? I don't advocate replacing any components just because, especially if there's a few non-invasive tests you can do to test your assumption, it could save time.

Where is the suspect cap in the circuit (across the woofer, in series with tweeter?) and how does the AC voltage compare between the good and bad speaker. Because a cap passes AC, there should be little or no measurable AC voltage across it (unless you got a deep bass music passage). If it has gone high impedance you will see lot's of bouncing around with occasional large numbers as you described.

Any photo's, schematics?
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Old 30th September 2009, 04:19 AM   #6
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Default Celestion ditton 44's - caps?

Here is a pic' of the cross over. All of the solder seems to be good and there is no visual hint as to any fault. Might there be another reason for the failure?

Many thanks for you time and help - LB
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Old 30th September 2009, 05:26 AM   #7
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Quote:
Originally Posted by lorienblack View Post
Here is a pic' of the cross over. All of the solder seems to be good and there is no visual hint as to any fault. Might there be another reason for the failure?

Many thanks for you time and help - LB
hope the pic arrives!
Attached Images
File Type: jpg cross 1.jpg (241.0 KB, 216 views)
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Old 30th September 2009, 04:21 PM   #8
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Default Look here

Lorien,

Search and find the Thread in this Forum titled :-

celestion 66 needs Mid-range

started by:-

Mr_White

There are many pages in it and a lot about restoring old Celestion speakers of the vintage of yours is discussed,
including plenty on replacing the capacitors for cases where one actually wants the speaker cross-over to work
in the manner it was originally designed,
plus have the audible improvemments capable with carefully chosen modern capacitors.
__________________
Alan
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Old 5th October 2009, 04:31 PM   #9
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That orange electrolytic on the top looks a bit out of place. Do you think someones worked on it before?

Do you have access to some kind of signal generator? If not, there's apps for the PC that will create tones of different frequencies as .wav files. You could put together a CD with different tones on to help debug.

Taking voltage measurements across the caps with different frequency tones should reveal the problem. 80Hz, 800Hz and 3KHz will work. If you trace out the components and connections you should be able to reverse engineer the schematic.
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Old 5th October 2009, 05:45 PM   #10
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Thanks a lot! I'll investigate the problem that way, I believe my neighbour has a meter.
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