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Grounding problem

Original poster: Esondrmn@xxxxxxx I had some guests over the other night and was asked to fire up the Tesla coil for them. This is only a 3" diameter coil with a 15 kv 60 ma power supply but does put on quite a show. I was running it in the same configuration that has evolved over many hours of testing and tuning which always worked just fine - but it wouldn't run worth a crap. At one half power or less, I was getting intense sparks between the outer primary turn and the strike rail which only got more intense and more frequent as I turned up the power - to the point where I had to shut it down. Also was getting some racing sparks on the secondary and the safety gaps were firing. It was like the primary would ring up but I could not get the power out of it - like the coil was out of tune. I knew tuning was not the problem and assumed that a connection had come loose somewhere. Definitely disappointing - with an audience.

I worked on it today, measured the caps, checked all the connections, gaps, etc. Everything was just fine. It has been very cold here for a few weeks with most days not over freezing and down to maybe 15 degrees at night. I suspected that I might have a ground problem so I cleaned the outside connections and slowly poured about four gallons of hot water over the ground rods. The coil now works fine. Frozen, hard as a rock, dirt makes a poor ground.

When I used to run my large coil out in the driveway at about 7 kva, I would always soak the ground plane area for a while first. I have never experienced a ground problem with my small coil like this. Just goes to show - always run a demo for yourself a few hours before the guests show up.

Ed Sonderman