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In an attempt to increase the efficiency of tube coils, I first tried around 1991 what I called the "sputter mode" of operation by using a high value of grid leak resistance and capacitance to create a degree of grid blocking. This method worked, but was somewhat crude. Next I tried a method called "duty cycle control". This method made the TC "on" time shorter than the 60Hz positive half cycle, but it made the sparks dim. Finally excellent results were obtained by keeping the coil off for a variable (adjustable) number of 60Hz positive half cycles. I called this type of operation the staccato mode. Using this method, the sparks remain the same length, but the input power is greatly decreased, and the tubes run cooler. Also, interesting sounds and spark appearances are created. My original timer circuits were TTL based, but they suffered from RF interference at higher powers. I then switched to a 555 timer based controller.
Above is the schematic for my 555 timer based staccato controller for tube coils. It is based on a 556 timer design by Dave Sharpe This schematic must be used in conjunction with the actual Tesla coil schematic. I don't show the SCR here. The SCR is shown in the actual Tesla coil schematic. The circuit board should not be mounted too close to the Tesla primary, or RF interference may result, and adversely affect the coil's operation.
My new improved zero-crossing triggered 555 based staccato controller circuit: The circuit modifications can be found at this link to Steve Ward's webpage. Steve's recent staccato VTTC work is there also. I used the zero-crossing circuit from John Tebbs' STSG circuit design, and added it to the 555 staccato circuit.
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