08-20-2015, 09:13 PM
What 20 does is provide a RF ground for the ant coil and the secondary of the IF transformer. If you follow that buss it ends up at the 75 tube diode this provides the - DC voltage which controls the gain of the two circuits (ant and IF).This is called AVC automatic volume control or AGC automatic gain control. The more signal at the anttena the more - voltage that is developed. The more - voltage on the AVC line the less gain the mixer and IF amp will have.
Bottom line is if 20 was shorted the set would work fine but would not have any AVC action. If it was open then it creates a problem of low gain.
Pin 3 of the 6D6 (screen grid) should have hv on it and NOT be connect to the other pins. If 3 is hooked to other pins that's your short!
Terry
Bottom line is if 20 was shorted the set would work fine but would not have any AVC action. If it was open then it creates a problem of low gain.
Pin 3 of the 6D6 (screen grid) should have hv on it and NOT be connect to the other pins. If 3 is hooked to other pins that's your short!
Terry
