Staccato Controller Information

Within this page, I will discuss what I went through to get my staccato board working, how the staccato works in general, and how it performs with the coil.

Normally with tube coils using AC on the plate (realizing that tubes only conduct in one direction, so its actually a half-wave operation), the tube is only on during the + half cycle of the AC input. This has advantages over DC (note that doubled AC, via the diode and cap, is filtered DC, but rather a pulsed DC, half-wave) in that the duty cycle is reduced to about 50%. This is because the tube is only on for the + half cycle, rather than a continuous DC on the plate of the tube. So this allows longer sparks as you can put more power into each half cycle.

The staccato takes it one step further. Rather than it being on for 60bps (there are 60+ half cycles in 1 sec), you can vary it from 30 bps (remember, each bang is only the 1/120th of a second, the length of 1 + half cycle), down to some 1bps or less. This is done by sending the output of the board to a SCR or TRIAC, which in turn grounds the tube cathode in synch with the +60hz cycle. Since the human eye is always trying to complete things the sparks can still look continuous at 20-30 bps, or slow motion at lower bps. Its like the movie theater, the screen is only showing us 25 frames a second (I think) with black in between, but our brain smoothes it out, to look continuous. So lets look at what is happening. Normal AC gives ~50% duty cycle, then with staccato at 30bps, were only seeing 25% duty cycle! The advantage is obvious! We can now run the tube at higher voltages and currents (within reason!). What would normally make the plate red, will not even get red with the staccato. Since redness has shown to cause plate to grid arcs, the non-red plates can now be at a higher voltage with much less risk of arc-over. This, in turn, allows longer sparks, as the power is increased. Its very helpful.

Here is the schematic. Many thanks for development go to John Freau, Dave Sharp, and John Tebbs.