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feasible repair of model 10314 KEF,s?advice?

 
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2chanman
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Location: Stamford Connecticut USA

PostPosted: Thu Dec 08, 2016 10:42 pm    Post subject: feasible repair of model 10314 KEF,s?advice? Reply with quote

I have obtained a pair of model 10314 Kef's that need major repairs which I hope to effect myself if feasible. All 4 woofers are foam rotted but with intact voice coils. Both mid/hf units are "needy". One has an open tweeter voice coil, the other has a seized mid voice coil (magnet shift?). There are cast aluminum covers behind each mid which appear immovable even though the 3 nuts behind them are backed off. Also, the black plastic rings surrounding the mid's on the front panel act as though they will be destroyed by any attempt to remove them. I need advice as to how to remove the mid/hf covers and speakers without damaging them or the cabinets. I acknowledge that these speakers may be too far gone to repair, in that the mid/hf units probably are not repairable or available. I think I can manufacture new surrounds for the woofers (if I can get around those connecting central rods)
I would appreciate any forthcoming frank advice as to whether it makes sense to attempt repair of these orphans, as well as perhaps some tips on how to remove those mid/hf drivers without ruining them.
I am newly registered on this site. I am a Connecticut Yankee, a retired Electronics Technician with over 60 years experience in building and repairing audio equipment, plus lifelong interests in audio, amateur radio, and astronomy.
I look forward to meeting some of you here on this site.
Sincerely, Tuckerman S. Jalet tJaIet@yahoo.com
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speakerguru
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PostPosted: Fri Dec 09, 2016 9:21 am    Post subject: Reply with quote

Welcome to the forum.

I'm assuming that by 10314 you mean Model 103|4. Am I correct?

If so, you have aquired a very good pair of speakers, well worth repairing. My pair is on permanent loan to our local Am-dram group in our Village Hall. I have had to repair them twice in the last 30years. Don't run them with rotted foam surrounds as you run the risk of damaging the woofer voice coils.

You are correct in not trying to remove the black plastic trim from the mid units. They are screwed on from the back and are not part of the fixing. The back of the mid magnet is fixed to the cast alloy mid enclosure via a three legged plastic tripod. If the three screws are removed the mid should fall out the front. Use gravity to help if they are stuck after all these years.

Good luck.
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speakerguru
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PostPosted: Mon Dec 12, 2016 6:26 pm    Post subject: Reply with quote

I'm replying to your pm here as it may be of use to other 103|4 owners.

Now that you have the mid units out, you can dismantle further. The tweeter comes out after removing the central screw from the back of the plastic tripod. There is a centering washer stuck to the top of the mid magnet centre pole piece for re-assembly. If it has come adrift, this may be the cause of the mid voice coil seizure. You can re-glue and re-assemble using suitable thickness shim material, which you remove when the adhesives have cured.

If the washer is not the cause of the mid seizure, you can remove the whole mid magnet assembly from the back by removing the three M5 screws which hold it to the chassis. The magnet assy is located on the chassis with pins which are not adjustable. You may, however, find that removing and replacing the magnet using a shim inside the VC will centre everything up enough to free the VC. If not, the spider can be loosened using a strong solvent (like MEK) and then re-glued while the shim is in place.

I have no idea why one tweeter appears to have three wires. I expect the mystery will be solved when you dismantle and rebuild. Maybe they have been badly repaired before?

The faulty tweeter will have to be replaced. I don't ever need to find a speaker repairer Laughing so maybe others can chip in here with advice about repairers and alternative tweeter supplies. IIRC KEF in Maidstone will sell you a (very expensive) alternative Uni-Q tweeter, but you'll need to replace the pair if you want a stereo match.
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2chanman
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PostPosted: Wed Dec 21, 2016 10:25 pm    Post subject: repair of KEF model 103/4 speakers Reply with quote

to speaker guru:
I have determined that the tweeter positioning washer is not "adrift" in the mid/hf speaker, and removed the tweeter. Further, I have have taken out the 3 hex head screws that secure the tripod to the chassis. The magnet assembly can be moved slightly but not removed, as it is apparent that the mid voice coil former is solidly attached to the to the side of the pole piece or to the adjacent wall, probably with errant epoxy or glue used in manufacture. There is plenty of free space around most of the pole piece except where it is stuck to the former. I am sure it would come out effortlessly but for being inadvertently glued. Perhaps a solvent inserted into the glued area might free the former, but might also adversely affect the the former and voice coil assembly. I doubt that freeing the spider would facilitate alignment of the voice coil assembly because the assembly is locked in place by glue and cannot move laterally where glued. Any suggestions?

2chanman
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speakerguru
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PostPosted: Thu Dec 22, 2016 9:53 am    Post subject: Re: repair of KEF model 103/4 speakers Reply with quote

2chanman wrote:
....as it is apparent that the mid voice coil former is solidly attached to the to the side of the pole piece or to the adjacent wall, probably with errant epoxy or glue used in manufacture....


An interesting theory but very certainly wrong. The unit and then the finished speaker would have been rigorously tested before packing and leaving the factory. There is no part of the manufacturing process where adhesive could inadvertently get in the gap or on the vc.

Sorry to give you bad news but your speaker has been dropped and one or both of the magnet assembly bonds has failed. When that happens the magnet will go to its lowest energy state which is a short circuit. So, the vc is trapped between the pole piece and the top plate by the full force of the magnet. It is being pinched in place.

The unit is really realistically a write off. Only if you have infinite patience and resource, there is a way. You will only get the coil out undamaged if you demagnetise the magnet. This can be done with a large demagnetise or by getting the whole assembly to a high temperature, past the curie point for the ferrite.
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2chanman
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PostPosted: Thu Dec 22, 2016 9:47 pm    Post subject: repair of Kef 103/4 speakers Reply with quote

to Speaker Guru:
Thanks for your latest reply. I have had similar thoughts about the speaker being dropped and that it is beyond feasible repair. When I have worked on other speakers where magnets slipped, it has always been obvious visually. I have inspected with an eye loupe the epoxy joints between the magnet assembly and cannot find any sign of separation or lateral slippage between parts. None the less, I agree with, and accept your findings.
I appreciate your taking the time to advise me regarding the repair of these speakers. I guess their next home will be the local junkyard, though I may save the crossover networks.

Best wishes to you for the new year.

2chanman
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speakerguru
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PostPosted: Thu Dec 22, 2016 10:37 pm    Post subject: Reply with quote

Normally frowned on in this forum, I think in this case it might be best to dismantle and sell the good parts in order to finance the purchase of a good pair.

Good luck.
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2chanman
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PostPosted: Fri Dec 23, 2016 10:09 pm    Post subject: repair of KEF speakers Reply with quote

To speaker guru:
Thanks for your latest. Is there a venue to offer parts for sale through this forum? If not, any suggestions? Thanks.

2chanman
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2chanman
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Location: Stamford Connecticut USA

PostPosted: Fri Dec 23, 2016 10:29 pm    Post subject: repair of KEF speakers Reply with quote

To Speaker Guru:

Don't bother to reply to my latest. I found the part of this forum where one can offer parts for sale.

2chanman
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