The Turn Of The Century Electrotherapy Museum

Micrometer Spark Gap Power Supply

Pancake Coil powered by cigar-box tank circuit

Box contains 1650V 10mA transformer and .0315 mfd condenser @ 7kV.   [ (7) .22 mfd  1kV condensers in series]

Note the position of the conical adjustment - Gap is open 1/16".

As the cone is pushed or pulled the gap is adjusted - a 3" portion of the cone adjusts the gap by a maximum of 1/16".

Hints of what's inside...

Internal view...