 |
| NST Filter and Safety Gap |
 |
 |
| The NST protection circuit and safety gaps are absolutely vital in any Tesla coil, especially ones that uses neon sign transformers as their primary power source. If not installed, high frequencies and voltages will ring back to the secondary windings and short them out, blowing the transformers. For my coil I chose the 'Terry Fritz' version NST proctection filter which uses 14 Metal-oxide varistors (MOV's), 12 .0033uf/1600v capacitors, 12 10meg resistors, 2 1K/100 watt resistors, and 2 safety gaps. This extraordinary circuit performs very well. |
| I used a 1/2 inch poly cutting board as the base for the entire assembly, and mounted the 100-watt resistors on ceramic standoffs using brass L-brackets and screws. The circuit board contains the MOVs, capacitors, and resistors and is mounted to the base using plastic standoffs. |
| Computer mouse balls make great safety gaps! I removed the rubberized coverings with a hobby knife and drilled and tapped 1/4" holes in each. Steel shafts were threaded and then screwed into the mouse balls. Each shaft was inserted into a mounted aluminum block and held in place with a set-screw so the gaps can be adjusted. Screws and lugs in the blocks provide connections for the wires. |
| Here is the completed filter assembly mounted on the mid deck. |