UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Audio (record players, hi-fi etc)

Notices

Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

Closed Thread
 
Thread Tools
Old 14th Aug 2018, 10:10 pm   #1
Colourstar
Octode
 
Colourstar's Avatar
 
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
Default Any cure for a rubbing speaker cone?

Hello all, I'm working on a late 60s Ferguson consolette stereo record player which has been out of use for several years and quite possibly stored in less than ideal conditions too. One of the 15 ohm 8"x5" EMI branded speakers was found to be seized. Light pressure on the cone easily got it moving again but it is very obviously rubbing (and sounding 'orrible). There is no obvious damage to the cone or suspension. Are there any possible remedies or is a replacement driver the only answer?

Luckily the other 8x5 loudspeaker in the player is fine.

Many thanks,
Steve
Attached Thumbnails
Click image for larger version

Name:	Drivers1.jpg
Views:	154
Size:	95.9 KB
ID:	167564   Click image for larger version

Name:	Drivers2.jpg
Views:	161
Size:	101.2 KB
ID:	167565  
Colourstar is offline  
Old 14th Aug 2018, 10:25 pm   #2
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
Default Re: Any cure for a rubbing speaker cone?

The 'seized' was probably rust between the coil and the concentric magnet pole-pieces - you do suggest that it may have been stored in sub-optimal conditions, and any dampness is likely to cause rust.

Some people have had success by way of 'exercising' the coil for a few hours through feeding it with enough 50Hz AC to cause it to oscillate in and out over 1/2 inch or so in order to work-away the rust. Only problem here is that the rust particles are themselves magnetic and so are going to stay entrained in the areas where the magnetic field's the strongest! There's not really much you can do to get the magnetically-coagulated rust-dust out of the gap.
G6Tanuki is offline  
Old 14th Aug 2018, 11:50 pm   #3
GrimJosef
Dekatron
 
Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,310
Default Re: Any cure for a rubbing speaker cone?

One possible trick for cleaning debris out of the gap is to try adhesive tape. This is quite often suggested as part of a 're-coning' exercise. I imagine it's very much more tricky with the cone still in place. I'm afraid another thing to worry about is that if the outside of the voicecoil is rubbing then there is a risk that the enamel on the wire will be abraded away and partial shorting of the coil will occur. The best solution might be to remove the cone-and-coil assembly and see if you can then restore the shape of the coil. But if the coil is firmly glued to the basket then removing it might be very tricky to achieve.

Cheers,

GJ
__________________
http://www.ampregen.com
GrimJosef is offline  
Old 15th Aug 2018, 6:45 am   #4
crackle
Rest in Peace
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
Default Re: Any cure for a rubbing speaker cone?

Sometimes the rubbing is caused by a white compound which forms on the zinc treatment to the speaker magnet poles. If this is the case then it can be sucked out.
I have fixed this on permanent magnet speakers by first carefully removing the centre dust cap and placing the end of a round hose from a good vacuum cleaner over the round hole in the centre of the speaker, and then exercising the diaphragm by pushing the hose in and out whilst stuck to the centre hole over the speech coil.
Stop and check after a while and flex the diaphragm slightly sideways whilst moving it in and out in different directions to check where the worst, if any, of the rubbing is. continue to rub away any roughness causing the scratching, then try the vacuum cleaner again.
During this process air is sucked in through the inner bellows and down around the speech coil gap and then out through the centre gap. Because the gap is so small the air is travailing very fast and I believe it can also remove small iron oxide particles.
It doesn't normally matter too much if some of the enamel is rubbed away from the outer edge of the speech coil, so long as the speaker is not earthed.
The dust cap can be glued back on with a bead of PVA glue around the edge.

This process works especially well on energised speakers, but do it before energising them so that there is very little residual magnetism.

Mike

Last edited by crackle; 15th Aug 2018 at 6:53 am.
crackle is offline  
Old 15th Aug 2018, 12:32 pm   #5
Boater Sam
Banned
 
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
Default Re: Any cure for a rubbing speaker cone?

Its usually not too difficult to separate the coil sleeve from the cone, having unsoldered the pigtails first.
Then you can clean out the magnet and pole gap thoroughly, scraping and blowing the rust out, stick paper to finish off.
Centre the coil with 3 paper slips and reglue to the cone. UHU works well.
Done a few, tricky but possible with care.
Boater Sam is offline  
Old 15th Aug 2018, 8:56 pm   #6
Colourstar
Octode
 
Colourstar's Avatar
 
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
Default Re: Any cure for a rubbing speaker cone?

Thank you all for the replies. Some interesting ideas there. I'll have a go at removing the dust cap first, as Mike suggests, although it seems to be very securely bonded so I'll proceed with caution....

Steve
Colourstar is offline  
Old 15th Aug 2018, 9:18 pm   #7
Boater Sam
Banned
 
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
Default Re: Any cure for a rubbing speaker cone?

Try a little heat and unpick it with a scalpel.
Boater Sam is offline  
Old 19th Aug 2018, 9:47 pm   #8
Colourstar
Octode
 
Colourstar's Avatar
 
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
Default Re: Any cure for a rubbing speaker cone?

Happy to say that the speaker is no longer rubbing. I managed to partially remove the dust cap and gave it the business end of an appropriately vintage Hoover Constellation. There was no obvious corrosion or particles to be seen, even with a good light and a magnifier, but I suppose with the tiny clearance between coil and magnet, it doesn't take much.

Anyway, thanks again for the suggestions. All is sounding good and I can now reassemble the record player, ready for a 'Success Story'.

Steve
Colourstar is offline  
Old 20th Aug 2018, 10:13 am   #9
Edward Huggins
Dekatron
 
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,302
Default Re: Any cure for a rubbing speaker cone?

That's great news. A good job that old and powerful Vac did not suck the cone off!
__________________
Edward.
Edward Huggins is offline  
Old 20th Aug 2018, 5:16 pm   #10
crackle
Rest in Peace
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
Default Re: Any cure for a rubbing speaker cone?

Yes you have to ensure it is placed over the voice coil area where there is a lot of strength, and hold the hose very firmly in-line with the coil former.
If you put it on the diaphragm direct it would probably suck a hole in it.
Well done Steve.

Mike
crackle is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 12:56 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.