Figure 20 Test Of Injecting Signal at the Cathode. The grid of a triode is grounded. The grid also goes through a redundant 1 meg ohm resistor to ground. The cathode goes through a 750 ohm then a 240 ohm resistor to ground. There is a 470 u f 25 volt capacitor in parallel with the 750 ohm resistor. At the junction of the 750 ohm and 240 ohm one end of another 240 ohm resistor is connected. The other end goes to a point labeled input. From here on the description is identical to that of Figure 19 B. The plate goes through a 100 k ohm resistor to the source of an I r f 820 m o s f e t. The drain goes to plus 400 volts. The 400 volt line also goes through an 18 k ohm 1 watt then another 18 k ohm 1 watt resistor to the cathode of a 100 volt 5 watt zener diode. The anode goes to the cathode of another 100 volt 5 watt zener and the anode of this zener goes to the cathode of yet another 100 volt 5 watt zener. The anode of the last zener diode goes to ground. There is a 22 u f 450 volt capacitor in parallel with all three zeners. The junction where the cathode of the top zener, the plus side of the 22 u f capacitor, and the 18 k ohm resistor all come together goes through a 1.5 meg ohm then a 150 ohm resistor to the gate of the Mosfet. A 0.047 u f capacitor connects from the junction of the two resistors to the plate of the tube. The plate also connects through a 0.1 u f capacitor to the output. A 1 meg ohm resistor connects from the output to ground. This completes the description of figure 20.
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