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Scored lines on speaker voice coil former

Discussion in 'Electronic Repair' started by N_Cook, Jan 27, 2009.

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  1. N_Cook

    N_Cook Guest

    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.
  2. N_Cook

    N_Cook Guest

    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
  3. N_Cook

    N_Cook Guest

    There is no overheating , scoring or any damage to the coil or elesewhere
    just these lines.
    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
    "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
  4. Eeyore

    Eeyore Guest

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

  5. jakdedert

    jakdedert Guest


    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?

  6. N_Cook

    N_Cook Guest

    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.
  7. Franc Zabkar

    Franc Zabkar Guest

    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
  8. N_Cook

    N_Cook Guest

    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.
  9. Eeyore

    Eeyore Guest

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

  10. Franc Zabkar

    Franc Zabkar Guest

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

    - Franc Zabkar
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