Topband: Control cable black conductors

[Andy Ikin]

Dave G4GED Wrote on Feb. 22nd.


"Hi and thanks for reading.

I'm trying to splice a damaged (rodents) RX ant control cable.
It has 7 insulated, stranded copper conductors all inside a PVC jacket.
Problem is, when stripped of their insulation, 3 (black, brown and
green), of the copper conductors have become coated in a black film? So
to effect jointing and soldering, require cleaning.
I've tried IPA 170 and several contact cleaners but none remove it.
So far, only Emery Cloth will do the job but it's very difficult to
clean each strand without breaking some and therefore weakening the joint.
All the other 4 conductors are bright clean copper when stripped.
Could anyone tell me why some insulated copper conductors turn black in
this way and whether there's a better way of cleaning it off."


Dave,  maybe you could try dilute sulphuric acid or lime scale remover 
VIAKAL. The black residue on the copper is probably copper oxide.

If you end up replacing the cable run then use tined copper conductors.

73

Andrew G8LUG