Found it. This is the soldering machine I built about 20 years ago.
I used an old computer power supply to house the whole thing. This was a really old, large supply, long before the ATX standard. The enclosure was huge, but the circuit board inside was small, so there was plenty of room inside. I had to rearrange the internal components a bit to make room for the large transformer that provides the soldering power. The original power supply circuit is just there to run the fan. :roll: I bought the transformer from a salvage/surplus company that used to mail me their catalog, but I don't recall the name. It's huge and heavy and I'm sure very much overkill, but the price was right. I'll hope others can give some guidance on what to look for and where, since I'm not really that knowledgeable on electronics.
There is an on/off switch on the power supply enclosure that turns the unit on and gets the fan running, but there's also a foot pedal to switch the power to the soldering circuit when I was ready to solder. It makes it a lot easier to get things all lined up, put the contacts in the right place, hold things in position, then just press the foot pedal till the solder flows. The foot pedal is wired to the large transformer. As with the transformer, I don't remember where I bought the foot pedal switch.
I looked on eBay and found tattoo foot pedal switches for as low as $3.00. You want a "momentary" switch. When you press the pedal, it switches on. When you take your foot off, it switches off. There are others that turn on when you press them that stay on when you take your foot off. You have to press them again to turn them off. Since this machine works so fast, you want the momentary switch.
I also wired a dimmer switch into the soldering circuit to control the output. It probably wasn't the best solution, but it worked. Most modern dimmer switches are digital and might not work, but mine was an old dimmer, so it served the purpose.
I also pulled a 10 amp circuit breaker out of an old surge suppressor and wired it in for safety. The wiring is straight forward. Power comes in, goes to the switch on the enclosure, then to the circuit breaker, then to the dimmer, then to the foot switch, and finally to the transformer. The output from the transformer goes to the socket that the contact handle plugs into.
The picture below shows the inside of the case. You can see the size of the transformer I used. I don't know if it had to be that big, but I didn't have much information to go on at the time. I built this long before the internet really matured. I did a little checking while writing this, and it looks like there is a lot of information on the web now if you search for homemade or diy resistance soldering machine or unit or something similar.
I built the giant "tweezer" handles that hold the contacts from some thick plexiglas that had the right amount of spring. There are certainly easier ways to go about it, but I've always enjoyed this kind of work. My dad was a machinist, so I grew up with tools in my hands and learned to make whatever I needed.
The contacts are made from arc gouging rods. The rods are carbon inside with a thin layer of copper on the outside for good electrical contact. To hold the contacts in the handle, I fit brass tubing inside the plexiglas that had a slit down the middle, and put set screws near the ends to tighten the tubing onto the contacts. I stripped the copper coating from the ends of the gouging rods and shaped them to a taper with some sandpaper. The contacts slide far into the brass tubing so as they wear, I can slide them out a bit and reshape them many times. The brass tubing is soldered to the power cord I used to connect the handle to the power supply.
The machine I modeled mine after also had a two piece contact system. One contact was a pad that the part was put onto, and the second contact was a probe that was touched to the part where you wanted to generate the heat. I never made one of those since the tweezer style handle worked well for my purposes.
That's what I can remember off the top of my head. If anyone has questions, I'll try my best to answer them.
I did a little searching and found an instructable to make a light duty unit using a PC power supply to power the whole thing. Take a look at
Cold Heat Soldering. I also found commercial units available for anywhere from under a hundred dollars to over a thousand.
For more information, search the internet for resistance soldering, cold heat soldering, cold soldering, etc.
Dave
