For those of us who build brass/white metal kits, an RSU can be a useful but pricey tool, no substitute for a soldering iron, but useful for many small and/or intricate jobs. The best known version, only made in small batches more or less as demand requires is the London Road Models unit, quite a versatile bit of kit with the option of several different voltage/current settings, but accordingly is presently priced at £210+£16 P&P ('cos it's heavy!). That's a lot of dosh, you can build a 4mm model kit for less than that, and go a good way towards more than half the cost of a 7mm one, so anything that might save a good few bob is a welcome change. (especially for 'Tight*rses' like me!). So I decided to have a look around, and perusing t'internet, I came across a couple of American sites with suggestions of DIY versions using the transformer from a dead Microwave oven. Going down this route, you remove the entire secondary windings from the high voltage (2Kv) transformer, substituting 3 or 4 turns of heavy gauge welding cable (or similar) to give a 3-4 volt output at much increased amperage, depending on cable diameter/turns ratio. I didn't happen to have a deceased microwave to hand, so looking further and way past the American RSU's costing $400/$500, I came across a British Company called "Frost Restorations" who market tools for the Classic car restoration market, they do one at a much more wallet-friendly £99.99 including carriage on 24 hour FedEx, so I took the plunge, and this is what you get.