Thank you very much for your reply.
A few weeks ago I decided I needed a new soldering iron and spent £16 on a We**er iron from homebase. When I switched it on a blue noxious smoke came out from the material between the coil and tip. After a couple of minutes I switched it off. I later got a full refund.
After receiveing your email last Saturday I ordered a PS-900, it arrived yesterday and your differential pi board arrived today. This evening I assembled the connectors to the board, all works sweet as. No blue smoke. It took me a bit longer than your video but the result was excellent - I could not have done this with my old iron.
Just please don't tell the wife how much it cost - thanks