On Wed, 17 Nov 2004 10:09:08 -0500, Mark Jones <ab...@127.0.0.1> wroth:

        It's a tool just like a lot of other tools.  If you know what it is and
how to use it properly, you'll be pleased with it like I am.  If you are
clueless and expect it to do something it was never intended to do, you'll wind
up being disappointed.

        The cold heat "iron" is an example of what's know as a "resistance
soldering tool".  It has two carbon or graphite probes set side by side but not
touching.  The probes are each connected to either end of a voltage source so
that when the probes contact a conductor together, the conductor gets hot from
the current passing through it.  The conductor heats up but the graphite probes
stay relatively cool.

        I was trained to use resistance soldering tweezers when I attended a
NASA hand soldering school at MIT's Lincoln Labs many years ago.  Those tools
are mainly used to solder wires into multi-pin military style circular
connectors.  Those connectors have hollow solder cups where the wire goes and
the pins are sometimes very close together.  If you use a normal soldering iron
with a hot tip, you usually wind up melting the insulation on the already
installed wires and making a mess.  With the resistance tool, only the pin
you're working on gets hot and you don't melt any insulation.  Also, solder
won't stick to the graphite probes.  It only goes onto the pin and wire.

        The cold heat tool is powered by 4 AA batteries so the amount of heat
you get is somewhat limited.  It's great for up to 22 AWG wire, somewhat usable
up to 12 gage, and useless for soldering big pieces of copper like the heatsink
tabs on TO-220 transistors.  It works really well for resistor and capacitor
leads on PC boards.

        There is 6 volts between the two halves of the cool heat tip.  That may
or may not be a problem if you get the tip between two pins on an IC.  Most ICs
will tolerate 6 volts applied almost anywhere as long as that's the only source
of power applied.

        Put the tip down on the copper land area where you want a joint.  Press
the button to apply current.  Let the copper heat up, it does that very quickly,
and then apply the solder to the hot copper.  As soon as the solder wets the
joint, release the button and you're finished.

        Used properly, the cool heat tool works a treat!

Jim