[PortugalTV]

"So going by calculations, the DC at g1 is given by the voltage division by the contrast pot + the 1.8M resistor and the 4.7k to ground. With +a being 200V, this should be around 5.9V max at g1, when the contrast pot is at max. As my 1.8M resistor measures about 2 Mohm, the voltage is closer to 5V."

Hi again! the voltage will fluctuate depending on how much current is pulled by the tube's grid...its not just a matter of dividing voltage.....lets say you have a 200v b+ and then a 10meg resistor and nothing after the resistor...if you probe after the 10 meg resistor you will get FULL 200v because the DMM does not pull almost any current so no voltage is dropped across the resistor...hope it makes sense, if not let me know..

i would avoid headache and stick with the schematic's figures.
i dont believe the snow from the tuner will create dc offset. on sets that dont use grid bias (grid is at 0v and contrast pot acts on the cathode of video amp)the dc level at the grid of the video amp is zero with or without signal

you really should try to inject composite...any thing will do....cable tv box, playstation, dvd player, etc etc etc
or just ground the cathode of the crt

dont give up you already put much time on this one we want to see it alive