Definitely on the primary (110v) side. Just remember that the Variac does
NOT isolate the output from the 110v input. I'm sure your aware but thought
I'd mention it. The output of the soldering gun would be AC but the
charger, of course, is DC. I had considering building one but also using a
DC cap in the circuit to give it just a bit more "punch". I've not looked
inside one of the commercial units to verify if those are done that way or
not.
Respectfully,
Ron Moore

"mj" wrote in message
ups.com...
Hi Don,
Yeah...I had thought about using a soldering gun for the power pack.
But I sort of like the portability of the soldering iron that I already
have built. I have a foot control, but it is a simple momentary ON
(while the pedal is to the metal) or Off (foot off the pedal). The
thing is, this setup works. I am just not getting the current I need at
the end of the carbon. I am hoping to get some more replies before I
throw more money at this. I "think" a larger charger with a variac will
work. If you don't mind taking a look at this auction, I am looking at
this variac:

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1

This would go on a 12/30/75 amp charger something like this one from
Amazon:

http://www.amazon.com/gp/product/B00...nce&n=15684181

One of the things that I don't understand (I don't understand a lot of
what I am doing, this is only one of them) is which side does this go
on? The 110v or the 12v side? My guess is the 110v side.

Thanks for the reply.

Mike