11-09-2014, 07:06 PM
Yes, the voltages on the print are all messed up. The highest voltage should be on the plate pin 5, then control electrodes pin 4 and 3 are lower and finally the cathode pin 8 should be the lowest. Your measured voltages seem about right, although the control voltages on pins 4 and 3 are a bit high if you are measuring them with no station being received.
The control voltage is developed across the screen grid resistor of the 6K7 IF tube. As a station is tuned in, the AVC voltage on the 6K7 control grid goes more negative, causing the screen current to be reduced. As the current falls the voltage at the screen rises, and since this voltage is connected to the 6AF6 control electrode, the eye closes.
Check the screen voltage on the 6K7 as you tune in a strong signal. If there is little or no variation in voltage, then that's why the eye is not operating properly.
The control voltage is developed across the screen grid resistor of the 6K7 IF tube. As a station is tuned in, the AVC voltage on the 6K7 control grid goes more negative, causing the screen current to be reduced. As the current falls the voltage at the screen rises, and since this voltage is connected to the 6AF6 control electrode, the eye closes.
Check the screen voltage on the 6K7 as you tune in a strong signal. If there is little or no variation in voltage, then that's why the eye is not operating properly.
