03-22-2014, 09:34 AM
Joe, in his radio you will not see any negative grid voltage, as the grid is grounded for DC. The autodyne osc/mixer uses a cathode feedback circuit, and there is no grid resistor to develop negative bias.
[Image: http://www.philcoradio.com/tech/images/89v2_sm.jpg]
[Image: http://www.philcoradio.com/tech/images/89v2_sm.jpg]