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N_Cook N_Cook is offline
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Default Mackie SRM450 popwered speaker

N_Cook wrote in message
...
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 ?


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



Heated screwdriver worked better than I thought
http://home.graffiti.net/diverse:gra...crewdriver.jpg
Pic shows the original soldering iron heater,
for unknown model. The one used with flange ground
off , added silicone sleeved wire and PTFE covering
the heater, slid over the end of the driver shaft.
And one of the long screws, mm /10mm/ 20mm graph paper.
Used about 10 watts, could have gone higher as no
plastic melted onto the PTFE.
Drilled out the screw holes a bit for easier
assembly/ next disassembly , (will add star washers under heads)
Caproic smell came off - what do Americans use as
glue or filler for construction plastic ?
I only smell it with USA equipment.

While heating one 10 inch recessed screwhead, extracted
the previous heated one. Further general tip - slide some grommets
onto the second extracting driver to locate easily
on the head, for deeply recessed screws.

So the second of 2 Mackie SRM450 to have mechanically
broken tail at the voice coil.
Previous , different unit, bass driver coil broken
where the coil wire is deformed to flat for the tail.
Not the slightest trace of overheating on that one.
This one, horn , nearly at this tail juncture , the break marked B
below, half turn vroken away from the resin core, and again so trace of
overheating anywhere.
http://home.graffiti.net/diverse:gra...ckie_horn1.jpg
4 engineering bolts hold the diaphragm to the magnet
but it is set in plastic frame, although engineering plastic, presumably
can deform enough to catch something.

As there is a milled out recess R already there I intend
trying to take the + and - tails through the same
side, not diametric. Grinding a slot in the
aluminium ring to take some 3x3 plaited 46 swg wire as tail.
Replacement driver 130 USD , diaphragm 70 USD
so worth trying as presumably swap USD for GBP and
add some for here. Very little diaphragm movement
so should not foul anything.


http://home.graffiti.net/diverse:gra...ckie_horn2.jpg
http://home.graffiti.net/diverse:gra...ckie_horn3.jpg
http://home.graffiti.net/diverse:gra...ckie_horn4.jpg

Cone thing presumably just stuck to the metal,
fell away on removing the

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