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N_Cook N_Cook is offline
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Default Mackie SRM450 popwered speaker

Meat Plow wrote in message
...
On Wed, 10 Dec 2008 08:08:41 -0000, "N_Cook" wrote:

Blown horn - anything to check on , in the way of ultrasonic oscillation

as
went during normal use?
How to break the cab in 2 ? Deep recessed screws tightly bound in dense
plastic. I know , from similar situations, it is quite likely to shear

the
screws with the undoing torque required. Soldering iron heater slid over

the
end of the long shaft screwdriver to locally melt the plastic ? Dropped
power to it for enough heat but relatively low temp to penetrate the

length
of the screw ?


Don't use a powered screwdriver. As far as the blown HF driver I would
suspect a transient spike or just low quality materials.



It would seem to be a generic Mackie voice coil failure.
Their low quality technique seems to be a specific length of 0.07mm wire, in
this case, flattened to something like 0.02 x .2mm at either end. This of
course increases the resistance and acts as a fuse. When I touched that
broken free curve of wire, in the pic, it disintegrated. Only that had been
heat affected, nowhere else. Start winding with the flat at the " inlet"
position and then 25 turns later have to wind the ribbon part around the
former as a final part turn to reach the appropriate feed out point.
It was the same with a bass driver I previously saw. Little point in
replacing with same, spending silly money. If they want fuses in line then
there are far more sensible approaches.

--
Diverse Devices, Southampton, England
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