Animated gif of VTTC running w/20 inch sparks!
810 Power Triode info:
The 810 (Power Triode) is a three-electrode high-mu tube with a typical power output of 575 watts (ICAS) for Class C. Because of its high perveance the tube can be operated at high plate efficiency with low driving power and relatively low plate voltage. The plate and grid leads are brought out to terminals at the top and side of the bulb, respectively - a design which provides very short internal leads, low internal lead inductance, and permits compact high-frequency circuits. Maximum ratings apply up to 30 megacycles. This tube runs the filament at 10 volts at 5 amps. The thing that ruins a tube is to starve the filament emission capability by using too low a voltage. If the plate current, or peak output just begins to drop off due to reduced filament voltage, the voltage is low enough to shorten tube life. You can try reducing voltage just to that point, then increase it just enough to restore full peak output, and that would be the minimum filament voltage it would be safe to run the tube at.
This coil was based on the dual 833C; furthermore, took about 4 months to build. Wanted a smaller coil then the 833C VTTC; however, this coil is still a bit big for indoor fun so off to build a single 304TL! Tab on links below for more pictures of this little 810 coil! Enjoy pics.