powderized voice coil wires

[Krischu]

Hi. I'm new to this forum. I'm from Germany, so bear with me and my humble and clumsy english. I love JBL speakers for their excellent sound and design and loved them already in the sixties and sixties.

Now I collect these speakers and use them in bass and organ amplifier equipment and such.

From time to time I buy a speaker and even succeeded in repairing some. My first reconing project will start soon. That's why I joined this forum - to gain some insights and participate in the experience and skill of others.

Now to the point:

I had two speakers during the past two years, one D120F and a D110F which both suffered from the same symptome: A hi-impedance voice coil. Examining that in detail I found on both speakers, that they had an interrupted voice coil wire right after the rivet (or solder lug) in the cone.
Scraping cautiously away the black glue - what material is that by the way? (footnote 1) - a white powder (instead of an aluminum wire) came to the light of day.

As if the aluminum had powderized itself (oxidized?) or reacted with some other chemical under the glue. I laid free a piece of the wire and wrapped a small spiral of copper wire around it and resoldered it to the rivet. (Soldering aluminum is critical, anyway - see footnote 2)

I would like to know if this problem of rotten wires is known or has been addressed in the past.


Thank you.

Christoph

Footnote 1: What liquid/glue is used to cover the voice coil wire on the cone surface?

Footnote 2: Is there any flux resin or something recommended to get these
aluminum voice coil wires soldered ? (I understand that voice
coils come with the wire ends tinned)

[John W]

Great question. I have seen the same with a pair of 2110s, a break just where the aluminum voice coils are soldered to the lead wires on the cone. My solder wasn't much good on the aluminum either.

[norealtalent]

Theres special solder for aluminum. Standard solder will not stick. I learned about it working on some Magnepan's. Aluminum does oxidize and turn to powder eventually. Copper doesn't last forever either but...:bouncy:

[jbl_man_uk]

I Have come across similar problems with HF diaphramms removed from 2441/2445/2420 etc that have been used in niteclub - disco enviroments..the copper filament lead-in wire (which is a tiny flat wire encased in a plastic covering,similar to a tiny computer ribbon wire)...the copper goes very dark and degrades to a black powder,no longer conducting thus causing the diaphramm to stop working.the actual diaphramm and voice coil is still OK and tests fine...i have tried various fixes,with some sucess...but does anyone know of a source for the correct flat-profile ribbon wire?

[Krischu]

Hi. I'm new to this forum. I'm from Germany, so bear with me and my humble and clumsy english. I love JBL speakers for their excellent sound and design and loved them already in the sixties and sixties.

Now I collect these speakers and use them in bass and organ amplifier equipment and such.
....


Oh my, I meant sixties and seventies, of course. :banghead:

[Mike Caldwell]

Hello

Some voice coil windings used copped clad aluminum wire so that it could be soldered. Aluminum is used in som cases because it is lighter in weight than a coil of copper would be and dissapates heat faster. Bostick glue was standard in JBL recone kits.



Mike Caldwell