Figure 3, Improved Williamson inverter Without the driver circuit. The input goes to the top of a 500 k ohm pot. The bottom is grounded. The wiper goes to one end of a 0.033 microfarad capacitor. The other end of the cap goes to the grid, pin 7 of a 12 D W 7 / 7247. There is a 470 k ohm resistor from pin 7 to ground. The cathode, pin 8, goes to ground through a 1000 ohm resistor. Pin 8 also goes to a connection point labeled feedback. The plate, pin 6, goes through a 270 k ohm then a 150 k resistor to plus 400 volts. The junction of the two resistors goes to the plus side of a 22 mike 450 volt cap. The negative end is grounded. Pin 6 of the 12 D W 7 also goes directly to pin 2 of the same tube which is the grid of the second triode. Pins 6 and 2 also go through a resistor labeled R sub C and a capacitor labeled C sub C to ground. Both components have the note see text. The cathode of this second triode, pin 3, goes through a 22 k ohm 1 watt resistor to ground. The plate, pin 1, goes through another 22 k ohm 1 watt resistor to plus 400 volts. The plate, pin 1 goes through a 0.1 mike cap to output 1. The cathode, pin 3, goes through another 0.1 mike cap to output 2. There is a 100 k ohm resistor from output 1 to a point labeled bias. Another 100 k ohm resistor goes from output 2 to the bias point. There is a note near the two output terminals which reads, quote, To grids of output tubes. End quote. There is a legend on the diagram which reads, quote, V o = 17 v, t h d 1 = 0.63 %, t h d 2 = 0.60 %, V o = 25 v, t h d 1 = 0.83 %, t h d 2 = 0.78 %, gain = 50, f 2 = 127 k c. End quote. End verbal description.
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