Figure 19, detailed schematic of minus 300 volt regulator contained in HP 712B rack mount regulated power supply. This power supply has two outputs. One is fixed minus 300 volts and the other is zero to 500 volts adjustable by a large knob on the front panel. The current rating of the minus 300 volt output is 50 mA while the 0 to 500 volt output has a rating of 200 mA. In this simplified diagram the rectifier filter circuits are represented by batteries. The battery labeled E2 is indicated as having a voltage of 505 volts. Its negative terminal is connected to the minus 300 volt line. Its positive terminal connects to the plate of the pass tube 6W6GT. This point is indicated as having a voltage of 205 volts relative to common. The positive terminal of E2 also connects through a470 ohm resistor to the screen grid of the pass tube. The cathode of the pass tube goes to the common line. The grid of the pass tube connects through a 1.5 k ohm resistor to the right hand plate of V9, 12 eh X 7. The voltage at this plate is minus 27 volts. The left hand plate of V9 connects to common. The right hand plate also connects through a 470 k ohm resistor to the positive of E2, plus 205 volts. This plate also connects through a 2.2 meg ohm resistor to the left hand grid of V9. The two cathodes of V9 are tied together and a voltage of minus 122 volts is indicated. The two cathodes go through a 200 k ohm resistor to minus 300 volts. The left hand grid of V9 connects to the left hand plate of V10. The voltage is minus 123 volts. The left hand plate of V10, 12 eh X 7, also goes through a 390 k ohm resistor to common. The right hand grid of V9 goes to the right hand plate of V10. This plate goes through a 330 k ohm resistor to common. The cathodes of V10 are tied together and are at a voltage of minus 212 volts. They go through a 120 k ohm resistor to minus 300 volts. A voltage reference tube, V11, 5651, has its cathode connected to minus 300 volts. Its anode connects through an 80 k ohm resistor to common. The anode also connects through a 68 k ohm resistor to the right hand grid of V10. This grid also goes through a 510 p f capacitor to minus 300 volts. The left hand grid goes to the wiper of a 50 k ohm pot labeled minus 300 volt adjust. Screwdriver adjustable. The bottom of the pot connects through a 62 k ohm resistor to minus 300 volts and the top connects through a 179 k ohm resistor to common. A 0..5 u f capacitor connects from the left hand grid of V10 to common. The minus 300 volt line connects to the minus 300 volt output. The common line connects to the common output. This completes the verbal description.