Last year at ExpoEM North I treated myself to a London Road Models Resistance Soldering Unit. Yesterday I decided that it was about time that I set it up.
Opening the box reveals a big grey unit, a couple of leads, some carbon rod and a set of instructions. The big grey, rather heavy, unit has two leads coming out of the back, one with a mains plug on it and the other with a footswitch on the end. The two other leads plug into two of the four sockets on the front of the unit, different combinations giving different voltages. One of the leads, the red one, has a probe on the end and the other black lead is left bare for you to attach to your baseplate as you see fit. The carbon rod is to be shaped as desired and fitted into the probe, I chose to sharpen it in a pencil sharpener to produce a point. Here's the kit;
Not included is a baseplate which is left up to the purchaser to provide to suit their needs. The instructions suggest either mild steel plate or brass sheet. I used .064" brass from Eileens screwed to a piece of MDF with a bolt screwed into one corner for the black lead to attach to, the lead having an eyelet crimped onto it for that purpose (the black lead can be soldered in place instead);
How does it work? Well it uses 'the heat generated by passing a relatively large alternating current between two surfaces to be joined' to melt the solder and make the joint. The parts to be joined have to be pre-tinned (although solder paste can be used) using a conventional iron. The work is placed on the baseplate and the probe used to hold the part to be soldered in place, or placed adjacent to it, and the footswitch depressed to turn the unit on and provide the current. When the flux boils and the solder flows the footswitch can be released, leaving the probe on the job until after the solder has solidified. Taking away the probe before releasing the footswitch can result in arcing leaving unsightly marks on the workpiece. The power can be varied between 1 and 4.5v, although the highest setting will be far too powerfull for most 4mm work I feel.
Here's some scrap that I've been playing with, Ive been using some aluminimum kitchen foil between the work and the baseplate as sugested in the instructions to save the baseplate from getting covered in flux;
I'm quite pleased with it so far, the real test of course will be using it on a kit. I've bought this for adding detail and overlays to etched kits, not as a replacement for my trusty Antex or for assembling frames etc. The advantage for detail work will be having the heat localised, which means that nearby joints shouldn't come unsoldered, and that the probe can be used to hold the part to be added in place. Which has to be better than holding, for example, a bonnet catch in place with a cocktail stick whilst bringing an iron to it...