The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com Nine Inch Pancake Coil giving Nine Inch Discharges... 02. - 04. May 2009 I was using a new crude silicone mold I made to revisit (and re-pot) a Pancake Coil that I wound in late January of 2002. Frank was on the phone, and I connected the coil to my tuner to see how it functioned on low power.  I was surprised to get nearly 6" sparks with less than 100 watts. Went to Home Depot and bought some bargain bin wood... Made a box.  This time I took some care to put an on-off switch and a detachable mains plug... I even soldered together a $#(%(#$* MMC cap.  I hate soldering.  My circuit board was a piece of cherry moulding. The 1250V transformer is from a small TIG welding high frequency arc stabilizer (Miller).  Its a nice transformer built for industrial use - RF arc starting is nothing more than a continuous duty d'Arsonval coil coupled to the welding cable with some blocking caps to protect things.    Many thanks to Brian Foley for the caps, they are rated .22 mfd at 1kVDC...4 in series for .056 mfd at 4kVDC.  Tungsten Spark gap is from H. G. Fischer, mounted to G10 base. Indifferent spark post connected to one leg of primary / outermost secondary winding. After testing, found out I didn't put enough wax! Nice! OOPs... For safety of coil insulation, discharge is limited to 7".