Now that you figured out the plate voltage problem, I think that the sound IF sections need to be aligned. John is right, one of the beauties of this set is the fact that video and audio are seperate. This way you can align the sound section indepentant of the video section. To align the sound section you need an RF generator that can generate a 21.25MHz with some audio modulated like a tone or something. This set is one of my personal favorites and I'm quite eager to see a writup on your site about it.
Jonathan