Buzz in sound from video - a porthole

[kramden66]

If someone could please take a quick look at the schematic for this porthole , the 24g24/25 figure 42 , page 39

http://www.earlytelevision.org/pdf/Z...anual_TV-5.pdf

problem is a buzz in the sound from the video , adjustments of the sound seem to make very little difference only a little improvement , buzz control doesn't either , what does is if you turn the agc , the higher you go the more the buzz , if you go down to very grey the buzz is almost gone , if there are some capacitors in that circuit that would make a difference please let me know , i'm stumped and don't want to test every capacitor there , the paper / wax ones were replaced the discs haven't , the micas haven't , the ones that look like resistors haven't etc etc since they are normally good but i get the feeling one isn't
anyway thanks
mike