03-03-2016, 10:42 PM
Well something is screwed up as your 6A8 voltages are too low. Grid 1 should be -3 or -4 vdc. Grid 2 (which acts as the oscillator plate) should be up around +150vdc or better. Screen grid (p4) at 80vdc. Plate should be about 200vdc. No way your local osc is going to be running with these voltages you have.
The screen grid of the 78 should be much higher too. If those resistors check ok then either the 6A8 is shorted or there is a problem with one of those caps.
Voltages seem ok over in the audio stages. I'm suspecting that you have a bad connection between the plate or cathode pin and socket on the75 tube or the tube bad. Voltage is good but tube isn't drawing any current. I'm assuming that the heater in the 75 is lit. Try swapping the 6A8 with another and recheck the voltages to see if they come up.
GL
Terry
ps. Grew up a little south of you in Sandy Spring.
The screen grid of the 78 should be much higher too. If those resistors check ok then either the 6A8 is shorted or there is a problem with one of those caps.
Voltages seem ok over in the audio stages. I'm suspecting that you have a bad connection between the plate or cathode pin and socket on the75 tube or the tube bad. Voltage is good but tube isn't drawing any current. I'm assuming that the heater in the 75 is lit. Try swapping the 6A8 with another and recheck the voltages to see if they come up.
GL
Terry
ps. Grew up a little south of you in Sandy Spring.
