(Misspelled Subject corrected)
On Fri, 17 Apr 2009 04:14:40 +0100, Sandi wrote:

Some insulated multistrand copper wire is pre-tinned and a lot is not.

First, I apologize for such a long-delayed reply. Just recently resumed
USENETting after several years. The flaming was pathetic (and apparently
cross-posted, no less!). When I tried to delete the flame messages, the
Pan newsreader crashed openSUSE 11.1! Needed to reboot. Never happened
before... (Pan is typically very stable, ditto SUSE.)

Anyhow, the worthwhile messages brought a lot to mind. (I built my first
radio at 6, adapting a Meissner circuit, fwiw, and I'm 73.)

In my experience, untinned stranded insulated Cu wire is rare, and
probably meant for uncritical applications that use screw terminals.

Speaking of rare wire types, only once since 1942 have I ever seen two-
conductor cable (including line/mains power cords) that had no way to
distinguish which wire was which. Otoh, inside a Hammond tonewheel organ,
and (late 1950s) perhaps most electric-action pipe organs, multiconductor
cables had no wire ID. (I don't know about cables between consoles and
the organ proper, though.)

I didn't see any mention of fused tinned stranded Cu wire.
Although uncommon in my experience, it's nice to strip in a production
environment, yet the bonds between the strands are weak enough that they
break easily when the wire is flexed.

Coatings, whether tin, solder, or Ag, must be applied before the
individual strands are joined. Didn't see any mention of that.

I distinctly recall reading about relays (probably contactors -- for
power -- with Ag oxide/Cd contacts; iirc, those don't weld easily, if at
all, but that could be wrong.

Btw, thanks for the chemistry!

Was wondering about the term "cinch" -- whether that's a formal
engineering term; I knew them as "crimp" connectors, but I think
"compression fitting" might be the formal term. As many know, Cinch was a
company that made some fine products; dunno about its present status.
(Merged, to form Cinch-Jones, iirc, but what happened to C-J, I don't
know.)

An important point about reliable solderless connection schemes, including
properly-engineered [crimp] connectors, Wire Wrap [TM}, and Termi-Point
is that all make a "gas-tight" connection. The wire and the metal it
connects to are forced together under great pressure, typically deforming
the wire and maybe the other part as well, so the boundary between them
cannot be penetrated by gas (under ordinary circumstances, at least).

I once read that when an intermittent poor connection is suspect,
submerge the device (operating) into a vat of sulfur hexafluoride gas,
and if there's a non-gas-tight connection, it will open up!

Anybody for Cool-Amp, an electroless Ag plating prep. used for joining Cu
busbar? True, that's not for ordinary electronics, but, megawatt stuff,
more likely.

Mentions of Cu oxide reminded me of Cu oxide rectifiers, which were in
use long before Se, Ge, or Si rectifiers. Cu oxide rectifiers had low
forward drop, pretty sure, which helped in measuring low voltage AC.

(Anybody remember Mg/Cu sulfide rectifiers, btw? What was good/bad about
them?)

Apologies, and regards,

--
Nicabod =+= Waltham, Mass.
who never worked on megawatt electronics