Three tube superhet. The top, white, of the antenna coil goes to the antenna. The bottom, black, goes to earth and circuit ground. The bottom of the secondary, yellow, goes through a .01 mike cap to ground. The cap is physically close to the antenna coil. We will return to the yellow lead much later. The top of the secondary, green, goes to grid 3, pin 8 of the 12 S A 7 tube. The large section of the 2 section tuning capacitor connects from pin 8 to ground. The heater, pins 2 and 7, go to a source of 12.6 volts. The metal envelope of the tube and grid 5 are tied together inside the tube and come out to pin 1. The cathode, Pin 6, connects to the tap, yellow, on the oscillator coil. the tap is closer to the bottom than it is to the top. The bottom, black, of this coil is grounded. The top, green, goes through a 220 pf cap to grid 1, pin 5, of the 12 S A 7. This grid also goes through a 27 k ohm resistor to ground. The small section of the two section tuning cap is connected in parallel with the oscillator coil. Grids 2 and 4 are brought to pin 4. This pin goes through a 1 k ohm resistor to plus 125 volts. There is another .1 mike 200 v cap from plus 125 v to ground. Pin 4 also goes through a .1 mike 200 v cap to ground. Pin 4 also connects to pin 4, red, of the i f transformer. pin 2, blue, of the i f goes to pin 3, plate, of the 12 S A 7. The red and blue leads are the primary of the i f transformer. The top of the secondary, pin 1, green, goes to pin 4, grid, of the 12 S K 7. The bottom of the secondary, pin 3, Yellow, goes through a .01 mike cap to ground. This cap is physically close to the i f can. The yellow lead from the i f can connects to the yellow lead from the antenna coil. The cathode of the 12 S K 7, pin 5, goes through a 270 ohm resistor to ground. The heater, pins 2 and 7, connect to the source of 12.6 volts. Pin 1, shield, and pin 3, suppressor grid are grounded. Pin 6, screen grid, connects through a .1 mike cap to ground. Pin 6 also connects through a 1 k ohm resistor to plus 125 v. Pin 6 also connects to the red lead, pin 4 of the second i f can. Pin 2, blue, of the i f connects to pin 8, plate of the 12 S K 7. The top of the secondary, pin 1, green, goes to pins 4 and 5 of the 12 S Q 7. These are the diode plates. The cathode, pin 3, is grounded. The bottom end of the secondary is pin 3 on i f cans with pins. On those with wire leads this lead may be yellow or black. This lead or pin goes through a 100 pf cap to ground. This pin also goes through a 47 k ohm resistor to the top of another 100 pf cap and the bottom of this second cap is grounded. The junction of the resistor and cap goes through a 2.2 meg ohm resistor to the top of a .1 mike cap. The bottom of this cap is grounded. The junction of the 2.2 meg and .1 goes back to the two yellow leads of the antenna coil and i f can. The junction of the 2.2 meg and 47 k resistors and 100 pf cap goes through a 220 k ohm resistor to ground. The junction of the three resistors and cap goes through a .01 mike cap to the top of the volume control. The bottom of the volume control is grounded and the wiper goes through a .005 mike cap to the grid, pin 2, of the triode section of the 12 S Q 7. Pin 2 also goes through a 10 meg ohm resistor to ground. The heater of the 12 S Q 7 goes to 12.6 volts. The plate of the triode, pin 6, goes through a 270 k ohm resistor to pin 6 of the 12 S K 7. Pin 6 of the tube goes through a .01 mike 200 v cap to the output. A 4.7 meg ohm resistor goes from the output to ground. End of verbal description.
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