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Shielded mic cable corrosion issue

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Anonymous
January 25, 2005 4:59:11 AM

Archived from groups: rec.audio.tech (More info?)

I am making an audio cable from a used mic cable. It looks like a
decent enough cable: braided shielding, paper and cotton threads, and 2
signal wires in good condition. The shielding though, looks green and
feels waxy.

My question is: is it corroded and useless, or has it been treated in
some way and can it be cleaned so that connectors (1/4" jacks) can be
soldered on? If so: what would the appropriate solvent be?
Thanks for your help.
Anonymous
January 25, 2005 6:31:16 AM

Archived from groups: rec.audio.tech (More info?)

Hi Mike, I know what you mean and I tried it. I cut back 4 inches but
I saw no difference.
Anonymous
January 25, 2005 8:06:38 AM

Archived from groups: rec.audio.tech (More info?)

Hi Mike: I agree with your views. However, the original question was
asked to find out if maybe there is some sort of waxy corrosion
protection that can be removed so the cable can be put to good use. If
that would be mistaken for corrosion it would be a waste to throw the
cable away. If it IS corrosion, I have no qualms about buying new.
Thanks for your comments.
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Anonymous
January 25, 2005 10:57:42 AM

Archived from groups: rec.audio.tech (More info?)

I think I will. Thanks.
Anonymous
January 25, 2005 11:26:18 AM

Archived from groups: rec.audio.tech (More info?)

<portland@zonnet.nl> wrote in message
news:1106658398.616566.282850@f14g2000cwb.googlegroups.com

> Hi Mike: I agree with your views. However, the original question was
> asked to find out if maybe there is some sort of waxy corrosion
> protection that can be removed so the cable can be put to good use.

A waxy coating over green, corroded copper requires at least two steps.
First you get rid of the waxy coating with a solvent, probably
petroleum-distillate based, and then you get rid of the corrosion on the
copper with fine sandpaper (150 grit or so).

Seems like a lot of work given that when you're all done, you have an old
mic cable that might also be stiffening up.

> If that would be mistaken for corrosion it would be a waste to throw
> the cable away. If it IS corrosion, I have no qualms about buying
> new. Thanks for your comments.

Given what good mic cable costs, when in doubt, just buy new.
Anonymous
January 25, 2005 2:00:27 PM

Archived from groups: rec.audio.tech (More info?)

<portland@zonnet.nl> wrote in message
news:1106647151.629159.113960@z14g2000cwz.googlegroups.com...
>I am making an audio cable from a used mic cable. It looks like a
> decent enough cable: braided shielding, paper and cotton threads, and 2
> signal wires in good condition. The shielding though, looks green and
> feels waxy.
>
> My question is: is it corroded and useless, or has it been treated in
> some way and can it be cleaned so that connectors (1/4" jacks) can be
> soldered on? If so: what would the appropriate solvent be?
> Thanks for your help.

Just a thought, have you tried cutting the cable ends back just a bit,
corrosion may have just effected the exposed ends especially if its been
stored long-term in a non ideal situation i.e. salt atmosphere nearby ocean.
The green may be verdigris due to copper corrosion but I'm not sure about
that waxy feel.

Mike
Anonymous
January 25, 2005 3:01:45 PM

Archived from groups: rec.audio.tech (More info?)

<portland@zonnet.nl> wrote in message
news:1106652676.449601.19880@c13g2000cwb.googlegroups.com...
> Hi Mike, I know what you mean and I tried it. I cut back 4 inches but
> I saw no difference.
>
Hi,
The only other thing I can suggest is to carefully tease out the braiding at
the terminations and use fine emery cloth to remove the corrosion and tin
the ends prior to making a soldered connection. But is it really worth the
effort if it really is corrosion? What quantity of cable is there? Will it
be used in an important location where reliability is important? It may end
up as false economy by using corroded cable at all.

Mike
Anonymous
January 25, 2005 5:29:10 PM

Archived from groups: rec.audio.tech (More info?)

This seems the most likely explanation why the screen is green all
along the entire length of the cable. Also the green stuff is not
uniform enough (on closer inspection) to be lacquer as was also
suggested. I will not use the cable and just buy new. Thanks to all
for your contributions.

HarryD
Anonymous
January 25, 2005 10:19:01 PM

Archived from groups: rec.audio.tech (More info?)

>Hi Mike: I agree with your views. However, the original question was
>asked to find out if maybe there is some sort of waxy corrosion
>protection that can be removed so the cable can be put to good use. If
>that would be mistaken for corrosion it would be a waste to throw the
>cable away. If it IS corrosion, I have no qualms about buying new.
>Thanks for your comments.

You could try some form of solvent (e.g. acetone) on the braid, and
see if it removes the green coating. I'd be concerned that any
solvent which would remove a waxy coating might also damage the
insulation around the center conductor. If you do try a solvent, take
all appropriate safety precautions.

I've seen conductors and braid turn green over a period of time, in
wires and cables which were manufactured with certain types of PVC
(polyvinyl chloride) insulation. I've read that this is due to the
tendency of certain PVC formulations to "outgas" a small amount of
chlorine over a period of years - this excess chlorine combines with
the copper to form a patina of copper chloride.

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Anonymous
January 25, 2005 10:19:02 PM

Archived from groups: rec.audio.tech (More info?)

"Dave Platt" <dplatt@radagast.org> wrote in message
news:10vd6t5j5vah220@corp.supernews.com

> I've seen conductors and braid turn green over a period of time, in
> wires and cables which were manufactured with certain types of PVC
> (polyvinyl chloride) insulation. I've read that this is due to the
> tendency of certain PVC formulations to "outgas" a small amount of
> chlorine over a period of years - this excess chlorine combines with
> the copper to form a patina of copper chloride.

One of the worst cases I ever had of this was with Monster Cable.
Anonymous
January 25, 2005 11:22:54 PM

Archived from groups: rec.audio.tech (More info?)

portland@zonnet.nl wrote:

> Hi Mike, I know what you mean and I tried it. I cut back 4 inches but
> I saw no difference.

So it's probably not corrosion but a green lacquer coating.
Try soldering the bit you cut off and see if the coating disappears.
If not, scrape it with a razorblade.

--
Eiron.
!