N_Cook wrote:
Ron wrote in message
...
N_Cook wrote:
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.
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:gra...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.

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

"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.


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


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

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