Dark gray soot on failed wire that broke - what is it?

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Hi - I repaired a broken laptop power cord last night. The cable consisted of a center conductor with PVC insulation and then a braided conductor around the outside of the PVC, and then a jacket on top of that braid.

The braid had completely broken due to (I'm assuming) excessive flexing. It broke right at the connector's strain relief.

What was interesting to me was that the broken strands were all covered in a gray powder that rubbed off on my fingers. What is this material and what reaction causes it?

Thanks!

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The grey powder is not quite black powder. It causes the smoke when electronic things fail. Black powder causes the bang. Maybe its just the lubricant they use when making the cable?

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Kartman wrote:
The grey powder is not quite black powder. It causes the smoke when electronic things fail. Black powder causes the bang. Maybe its just the lubricant they use when making the cable?

The powder was present only where the shield had broken. I cut out the broken section and rejoined the cable, and the non broken sections did not have this powder.

Alas, no magic smoke was ever released with this cable. It just stopped functioning. Releases of magic smoke are much more exciting.

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How about a Wild A.. Guess...

Aluminum Oxide.

I suspect as the cable failed the full current load was being carried by fewer and few strands of the multi-stranded shield.

The thin wires overheated, and oxidized, as they essentially "burned up", albeit without any puff of black smoke externally.

JC

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Kartman,

Thank you

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My laptop PSU cable failed in a very similar way. It's a bit sad.

But as for what that substance was is it not just carbonzied metal - take the power connector from your car battery and then drag it over the contact so that it arcs. You get smoke and black powder - surely that's the same thing?

While my own laptop cable was failing it used to "crackle" and get so hot I couldn't touch it. How this passes safety certification is a complete mystery?

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Quote:
Aluminum Oxide.

Sure..It is.

Jeckson

נרגעת

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Hi Michael,
I repaired a power supply like that a few years ago. It also had the grey powder material, which I put down to a "mixture of copper, tin & ground up PVC". When the wire breaks due to flexing, there has to be small amounts of copper & tin and the abrasive action of the wire on the PVC would be scraping PVC as it is being flexed. If I recall it was a Dell PC, power supply.

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?