Don Foreman wrote:
On 23 Aug 2005 13:58:15 -0700, "
wrote:


I got an email response from the customer support. The guy said the
spoke with production and they told him it was possible to get to the
pin in question by using a dremel tool on the expoxy potting. The pin
seems to be broken within the wall of the speaker (about 5/8 inch
thick, corian like material). I've carefully dremelled enough material
away(about 1/2 inch depth) to see a bit of the rest of the pin.

Now I'm taking a break before I screw things up. I understand that one
can really f**k things up with a dremel tool.

I've ordered a replacement pin through a dealer so I can see what I'm
dealing with.

What I think I might do is get some more of the pin exposed and find a
place where I can place a proper solder point. I would then cut the
original pin at that point, cut the replacement pin to match and solder
them together. I'm sure this will be stronger than what I'm doing now
since when I pull the pin out in it's current state of disrepair there
is solder bonded to the external portion which I heated; it appears the
solder is not well bonded to the stump embedded in the speaker,
probably since that part isn't hot.


I looked at the pictures. Looks like the material is copper. Are
there any threads on the stub at the bottom of the hole? If you can
dremel out enough material, a new part could be made that has a
drilled and tapped hole to engage the threaded (?) stub. Three
threads would be enough.

If the replacement part were knurled on the outside and the hole was
then backfilled with epoxy after the part were screwed onto the stub,
I think you'd have a repair that would be sound both mechanically and
electrically.

I would make the replacement part of brass, rather than copper.
There's enough cross-sectional area that the resistance would still be
negligable, and it would be somewhat stronger than copper.

This could have a spade lug rather than be a binding post, if you
like. I could plate it with tin or nickel -- or gold, if you
wanted to buy the juice.

From the photos, I'm thinking there's a nut back there, one of two
securing the double binding post to that "Corian like" stuff he
mentioned. Could well be something just like the "Vampire BP2" a ways
down on this page:

http://www.welbornelabs.com/speakerstuff.htm

And, screwed into the nut is the remaining male threaded part of the
busted post, with a wire soldered to it's back end in typical binding
post fashion. Or, maybe they used a solder lug under the nut, with the
speaker/crossover lead wire soldered or crimped to it, in which case
removing enough of the plastic ought to let you access the surface of
that solder lug.

If they didn't use a solder lug and he drilled into and peeled out the
existing threaded stub to to be able to screw something into the threads
of that nut, he'd likely disconnect the back end of the stub from the
nut. I don't like that.

I'll raise my voice again and scream CONDUCTIVE EPOXY! I think I showed
a couple of days ago that the added series resistance would be
insignificant.

I (who can spend three hours fashioning and splinting on a replacement
foot of an antique ivory asian "medicine lady", missing when I bought
it) can appreciate why the OP eants to keep the original appearance of
his speaker by connecting a pigtail lead with conductive epoxy as I
suggested, even though I think that's the best way to avoid fracturing
the conductive epoxy when connecting a lead to the speaker.

My "second best" suggestion is to reconnect the present broken binding
post back onto whatever metal is there *without* trying to drill into
it, and use conductive epoxy to make the connection.

I'd suggest Dremeling a couple of "keyways" into the existing plastic
binding post base because it's likely to be made of some thermoplastic
epoxy won't like to stick to, and there's a fair amount of torque
exerted when the binding post finger nut is tightened. (Maybe even
enough to be what caused that busted post in the first place?) I'd use
enough conductive epoxy to make the connection and squeeze up around the
post, removing whatever bubbles over.

Whatever method he ends up using, he'd better be gentle about tightening
the finger nut on that post. Using bannana plugs on the end of the
speaker leads might be the safest choice.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."