SpeakerTalk Forum Index SpeakerTalk
This forum has been set up to facilitate discussion of 1970s KEF speakers and drive units. The owner of the Forum has no connection with KEF Audio.
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Corellis

 
Post new topic   Reply to topic    SpeakerTalk Forum Index -> KEF Speakers from the 1970s
View previous topic :: View next topic  
Author Message
tolstoy
Junior Contributor 10+


Joined: 31 Aug 2005
Posts: 16
Location: London

PostPosted: Wed Aug 31, 2005 9:55 am    Post subject: Corellis Reply with quote

I have a pair of these animals which have been sitting in my cupboard for a number of years now following the failure of the T27 tweeters. I acquired them many years previously in a similar condition, both units were dead. I eventually got round to having them rebuilt by KEF, however after several months they again blew. End of story. Start of dust gathering. I love the sound of these beasts and really want to put them back on the road but need to figure out what the problem is here. My guess is that the crossovers have deteriorated over the years and need replacing. Having looked at the SP1052's one component does indeed seem to bear this out with what appears to be a degree of oxidation (well, its a green mould type stuff, I'm no expert here). Would I be correct in my thinking and are they directly replacable with the same component, a modern equivalent or can I just swap out the offending 'thing'. I'm confident with a soldering iron but would need to know what the 'thing' is. Also I need to repalce the T27s, is this a problem?

Thanks in advance for any help you can offer.
Back to top
View user's profile Send private message
ColinR
Über Contributor 1000+


Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Wed Aug 31, 2005 11:44 am    Post subject: Reply with quote

Quote:
green mould type stuff


Bet the components a green resistor and it's fluffy as well, due to corrosion caused by bacterial activity in the foam damping releasing acetic acid Cool .

Blowing tweeters is down to an underpowered amplifier "clipping" and sending distorted square waves with high harmonic content through treble drivers.
OR
A stuffed series bass inductor allowing low frequency signals into the treble section. Highly unlikely with the Corelli as the bass unit will blow long before the inductor.
OR
An unstable amplifier design that "motorboats" and produces high frequency oscillations.
OR
Faulty output transformers on a bottle job.
OR
Several other amplifier fault conditions allowing a dc output.

So how big is your amplifier? How old is your amplifier?

Good examples of T27's cost rather a lot on ePay these days.

Read the advice sheets in "hints and tips" and then talk to Malcolm Jones at Falcon Acoustics about buying a few capacitors.

The fluff comes off the resistor btw and no significant damage will have been done to the component.

Do buy two 0.5amp Polyswitches.
Back to top
View user's profile Send private message
tolstoy
Junior Contributor 10+


Joined: 31 Aug 2005
Posts: 16
Location: London

PostPosted: Wed Aug 31, 2005 12:48 pm    Post subject: Reply with quote

Wow. I'm impressed. Can't say I have much of a clue of half what you describe, 'motorboating', 'bottle job'? But your comments do help point me in a new direction. The amp I have is a pretty hefty Sony 90w TA-F630 esD from the 80's, however recently I have been experiencing dodgy contact on the phono stage, leading to blistering hum on occasions. This is fairly recent but perhaps could have been having impact on the speakers previously? From what you suggest I think I should sort the amp out first, then look again at the next step. Polyswitches? What do they do?

Again, thanks for the speedy and informative (well, if you explain the above terms it will have been) response:-)
Back to top
View user's profile Send private message
tolstoy
Junior Contributor 10+


Joined: 31 Aug 2005
Posts: 16
Location: London

PostPosted: Wed Aug 31, 2005 3:34 pm    Post subject: Reply with quote

Okay, I've discovered what Polyswitches do:-)
Back to top
View user's profile Send private message
ColinR
Über Contributor 1000+


Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Wed Aug 31, 2005 6:50 pm    Post subject: Reply with quote

Quote:
leading to blistering hum
~
Quote:
'motorboating'


That'll do, any constant "farting" noise due to dodgy earths or component failure.

Quote:
'bottle job'

~

valves. Owners of valve amplification are termed "bottleheads".

Need any more translations Smile ?
Back to top
View user's profile Send private message
tolstoy
Junior Contributor 10+


Joined: 31 Aug 2005
Posts: 16
Location: London

PostPosted: Wed Aug 31, 2005 8:28 pm    Post subject: Reply with quote

Learning is a great thing. eh? Smile I see there are T27's on ebay at about the cost I'd expect so I'm on the way to getting these guys back on track. You were spot on about the resistor by the way.

Thanks for your help, I'll be bookmarking you for the future.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    SpeakerTalk Forum Index -> KEF Speakers from the 1970s All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group