New project - Canadian RCA CTC 38

[maxhifi]

After watching the tv all year decided to give it some attention. I adjusted purity, convergence, and grey scale. Then I adjusted linearity and pin cushion. Man, does it ever make a nice picture now! I also replaced the nuvistor in the tuner,
which sharpened up the picture a lot. Only problem is the vertical position seems low (I.e. The black bar on the bottom of a 16x9 picture is narrower than the top bar when size and linearity are correct) and I have no clue how to adjust it. It's still got a bit of a wave as it did before, but I haven't changed any electrolytic capacitors yet. It's almost unbelievable how good the colour is now, it looks better than a lot of newer CRT televisions.

Also another question - an ideas what the blue knob just in front of the purity rings is for? (See pic)