Figure 28, A Power Supply for the Amplifier. As any self respecting power supply should, it begins with the plug that connects to the power utility mains. A polarized two prong plug is recommended. The wide prong connects to one end of the primary of the power transformer. The power transformer has a primary voltage that is correct for your country. The other prong of the plug connects through the on off switch then a 0.5 amp slow blow fuse, to the other side of the primary winding. The high voltage secondary is specified as 325 dash zero dash 325 volts at a minimum of 40 mA. It will do no harm to go higher. The filament secondary is specified as 6.3 volts at 2.5 Amps, 1.5 if you are planning to build only one amplifier. The anode of a diode, 1N4007, goes to one end of the h V secondary. The anode of another diode, same type, goes to the other end of the H V secondary. The two cathodes connect to point X. Point X connects to the positive end of a 100 u f 450 volt capacitor. The negative end of this capacitor connects to the H V center tap. One end of a 1.5 k ohm 2 watt resistor connects to point X. The other end connects to a point called B plus. B plus also connects to the positive end of another 100 u f 450 volt capacitor. The other end connects to the H V center tap. A 1.8 k ohm 2 watt resistor connects between B plus and pin 1, one of the anode pins, of V1, 0 A 2. Pin 4, one of the cathode pins, connects to pin 1, anode of V2, 0 B 2. Pin 4, cathode of V2, connects to ground. Pin 1, anode of V3, 0 B 2, also connects to ground. Pin 2, cathode of V3, connects to the H V center tap. There is a 12 k ohm 5 watt resistor connected between pins 5 and 7 of V1. Pin 5 is the other anode pin and pin 7 is another one of three cathode pins. This places the resistor in parallel with the tube. A 36 k ohm, 1 watt, resistor is similarly connected between pins 5 and 7 of V3. Pin 5 of V1 connects to the 255 volt output of the power supply. Pin 5 of V2 connects to the plus 105 volt output point. Ground of the power supply connects to ground of the amplifier. Pin 4 of V3 connects to the minus 105 volt output. The 6.3 volt winding is connected as follows. A 100 ohm resistor connects to one side of the filament winding. The other end of this resistor connects to another 100 ohm resistor. The other end of the second resistor connects to the other side of the filament winding. The junction of the two resistors connects to ground. There are three tubes in the amplifier, 12 A X 7, 12 A V 7, and 12 A U 7. Pin 9 of all three tubes connects to one side of the filament winding. At each tube socket pins 4 and 5 are tied together and then connect to the other side of the filament winding. Wires from the power supply to the tube filaments, and between tubes, should be twisted together.
End of verbal description.
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