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Scored lines on speaker voice coil former

N

N_Cook

Jan 1, 1970
0
Due to dirt in use or at manufacture?
Carlsboro 10 inch ,open circuit, so burrowed in to explore. On the phenolic
cylinder that is the former for the voice coil . 4 pairs of scored
ines( stand out white against the amber colour of the phenolic). Each pair
about 6 to 7mm apart and arranged pairwise diametrically.

I suspect 4 pieces of sharp edged metal shim used in the original cone
setting and scored on removal. All the lines go axially , fully from one end
to the other , so if made in use would require the diaphragm (spider?) being
driven 10 mm into the magnet housing. Apart from the nearly symetrical
distribution of the lines.
 
N

N_Cook

Jan 1, 1970
0
Ron said:
Something isnt right here. Are the scored lines on the inside or the
outside of the coil former? Are the windings damaged by the scoring?
If it were the setting shims to blame for the scored lines - which seems
doubtful they`d use metal, all mine are plastic - they go on the inside
of the coil former. The windings are on the outside.

Take photo if you can.

Ron(UK)

the lines are on the smooth internal surface that glides over the central
section of the magnet, not the coil surface.

I doubt the lines are anything to do with the failure, that is well outside
the coil area. Probably due to stress on epoxy curing on a supposed stress
relieving bend of the coil runout wire inside a fillet ring of epoxy where
the cone meets the phenolic cylinder and before the join with the pigtail,
so repairable.

Will try a pic of the lines
 
N

N_Cook

Jan 1, 1970
0
Ron said:
Something isnt right here. Are the scored lines on the inside or the
outside of the coil former? Are the windings damaged by the scoring?
If it were the setting shims to blame for the scored lines - which seems
doubtful they`d use metal, all mine are plastic - they go on the inside
of the coil former. The windings are on the outside.

Take photo if you can.

Ron(UK)

There is no overheating , scoring or any damage to the coil or elesewhere
just these lines.
http://home.graffiti.net/diverse:graffiti.net/voice_coil.jpg
Could someone confirm that the woven and corrugated yellow part I've
labelled purple "S" is called the spider. The cone is to the other side of
it.
"L" is the lead out of the coil and "G" is some sort of optical guide laid
in the layup, on the manderel, of the phenolic for placing the lead-outs to
then meet up with the pigtails at the cone. Moire fringing is where the coil
is. A second sight guide and second of a pair score line is part in shadow
off to the upper right.

There is a third and fourth pair of lines diametrically opposite these 2
pairs
 
E

Eeyore

Jan 1, 1970
0
N_Cook said:
Due to dirt in use or at manufacture?
Carlsboro 10 inch ,open circuit, so burrowed in to explore. On the phenolic
cylinder that is the former for the voice coil . 4 pairs of scored
ines( stand out white against the amber colour of the phenolic). Each pair
about 6 to 7mm apart and arranged pairwise diametrically.

I suspect 4 pieces of sharp edged metal shim used in the original cone
setting and scored on removal. All the lines go axially , fully from one end
to the other , so if made in use would require the diaphragm (spider?) being
driven 10 mm into the magnet housing. Apart from the nearly symetrical
distribution of the lines.

How much time do you waste inflating customers' bills by wasting time on the
pointless ?

Graham
 
J

jakdedert

Jan 1, 1970
0
Eeyore said:
How much time do you waste inflating customers' bills by wasting time on the
pointless ?

Graham
Graham,

Since you've discovered this group, you've done just as little to
contribute as you do on any other. Why don't you just go to bed...and
stay there?

jak
 
N

N_Cook

Jan 1, 1970
0
Ron said:
Yes the rear suspension is traditionally refered to as the spider
because in early speakers it was a (usually) three legged tufnol affair
a bit like the '3 legs of Man' mounted insided the v/c and screwed to
the pole piece of the magnet. The v/c was centered by loosening off the
screw and moving the spider around. Often a low frequency (100 hz) (120
in the USA) note was played through the speaker whilst the adjustment
took place



I dont think that line G is any form of optical sight, just where the
layup of the laminations of the former are recessed to feed the lower
coil leadout up


I think those are just marks made by withdrawing the coil former from
whatever chuck held it in the winding machine or curing oven - or both.

If there`s no rubbing or burning of the coil, you`ll probably find the
o/c is where the end of the coil passes throught the cone and is
soldered to the pigtail. This is sometimes repairable by scraping off
the glue and reheating the 'blob'. Not worth messing around tho,
replacement speakers like those are cheap.

Ron


If it was scoring from expandable/contractable mandrel or a chuck of some
sort I'd expect it to be engineered and pairs of lines exactly 6mm or
something precise apart, these are about 6 to 8 mm apart and some lines have
a nearby accompanying line. They are white as in scoring not grooves set in
at moulding . Or more likely no marks as what is the point if the process
leaves such serious imperfections where you don't want them.
 
N

N_Cook

Jan 1, 1970
0
Franc Zabkar said:
I've often encountered speakers which sound distorted but are still
functional. By moving the cone by hand, I can feel and hear the coil
scraping against something. Would this be caused by blistered
insulation as a consequence of overheating?

- Franc Zabkar


Any bits of swarf or grit, causing lines in service, would be only
half the length of these lines. They extend the whole axial length of the
coil former, into the dome space.
 
E

Eeyore

Jan 1, 1970
0
jakdedert said:
Graham,

Since you've discovered this group, you've done just as little to
contribute as you do on any other. Why don't you just go to bed...and
stay there?

I discovered it a long time ago and I contribute useful information. N_Cook however
is a twat. He is a self-admitted 'bodger'.

Graham
 
F

Franc Zabkar

Jan 1, 1970
0
A 'skippy'? do explain please

Ron(UK)

A Skippy is an Anglo-Celtic Aussie. I always thought Eeyore was a Brit
living in Britain.

- Franc Zabkar
 
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