I think a pistol type solder gun can be easily adapted into a center pin zapper. The cheap one that I have is a 65 watt model. It puts out around 130 Amps at ½ volt. I made probes out of some copper wire, but brazing rod would be better, and zapped some old flanges. At full power it took seven mississippis to produce smoke. When plugged into my light dimmer outlet, which I use for regulating the heat on the shank bender and on the hammer iron, and turned down for ¼ volt output it took 40 mississippis to produce smoke.

Of course a solder gun could be dismantled and all kinds of probes and bell and whistles could be added. For instance, the temperature of the pin will be proportional to the change of current while it is being heated. Resistance increases along with temperature. An ammeter installed on the 120v side could be used to regulate the temperature.

I wish I had had a zapper on a certain spinet that had sluggish whippen flanges. I can imagine that using a solder gun with brazing rod probes of the right length and wedge shape could have worked well with the action in place.
Jeff Deutschle
Part-Time Tuner
Who taught the first chicken how to peck?