I spent some time this past weekend fixing my Tesla coil named Zeus. It is a 450W SRSG (synchronous rotary spark gap) coil that can usually produce sparks up to 800cm. Around a month or two ago I was running the coil, having just replaced the transformer (an old Franceformer), when a capacitor failed. The capacitor might have failed due to bad timing on my spark gap (some adjustment will be necessary in the future), or due to my gross oversight in the original design. The original capacitor bank was designed such that the first capacitor and last capacitor in the series were very close to each other. The potential became great enough that the first capacitor failed in a spectacular display of electrical arcing to the leads of the last capacitor.
I have since overhauled the entire capacitor bank, changing the design to keep distances maximized. While I was finishing the capacitor bank I decided to go ahead and overhaul the entire coil's wiring. Prior to the decision I had been using crimp terminals to connect wires on the coil. These shoddy connections caused the coil to be very unreliable. A demonstration item like a Tesla coil should work perfectly every time. To have it fail as a result of bad connectivity is disappointing.
After finishing the overhaul of the capacitor bank and the coil wiring I was ready to test. Usually when testing the coil I can count on the thing to refuse to start for a bit. Often it starts at around 80-90VAC as read on a variac, however, with the recent improvements the coil consistently started around 40V. I was able to achieve sparks at this voltage which was a first.
I expect that I will not have trouble with starting the system. Next I will need to develop a better spark gap but until then...