Not made for the UK climate, stored in a (normal for UK) damp garage for 3
years, came out making nasty "amp clipping" noise.
Now it is totally apart, small bits of aluminium oxide in the voice coil
slot were causing the distortion along with loose skirt biased to one still
retained side. 15 inch size with aluminium basket.
The voice coil is in perfect condition and no imperfections to the cone
despite 30 years old.
Prior to me getting to look the owner had removed the 3 magnet retaining
bolts and removed some perished foam filter from inside under the mesh cover
and squirted in WD40.
The white oxide formations had burst the glued skirt off , about 80 percent
of its rim, and the same for the cone rim (after removing the periphery
bolts) and nothing much holding on the remainder, easy to prize off.
At the moment intend masking off the central voice coil slot area before
abraiding back the lands to take contact adhesive to replace the skirt and
cone. Then air blast and run thick plastic around the slot to clear any
crud. The magnet does not seem to be corroded, shiney, no obvious rust
spots.
Any tips re added ptfe film, gluing sequence, positioning/algnment, what
sort of foam to add as he threw the original away? etc.

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Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/