The Turn Of The Century Electrotherapy Museum
(C) Jeff Behary 2007

15kV 60mA Bipolar Pancake Coil Test

Here is half of the cottage museum room.

The box is built from Brazilian Cherry.

Two 9" Pancake Coils, flat spiral variety.  These coils are unusual because they contain less than 200 turns of wire, making them a very high frequency coil.

The secondary coils are terminated in rubber coated wire rather than a normal discharge post.
The discharge posts are external, the respective wires connecting to each post.
This unusual approach was typical of what Tesla did for his table top units.  This prevents
strain on the insulation of the coil, not having a heavy object situated at the heart of the highest potential
where the wax is liable to crack.

Two .002 mfd 40kV doorknob caps were used in parallel. 

A 16-series 1/2" diameter tungsten spark gap was used.  Best performance was with
from 6 - 8 gaps.  When more gaps were used the discharge could grow longer, but sparks began to appear
on the top surface of the Pancakes.