[BrendaAnnD]

If you have audio at point C but not point D, the 6AQ6 is working. Whether it's working WELL or not is another question. If it were not, you would have no audio anywhere because it could not detect a signal. Point C according to the schematic I have, is the control grid of the 6AQ5 output tube (actually, there must have been more than one run of this model, because the Riders shows a series string set.) The lack of audio at point D could just mean the sensitivity of whatever you are using to test is not good enough. Check for audio at pin 3 of the output tube. Meanwhile, I'm going to see if I can find the version of the model that you have.