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it looks like the lin pot was taken out of circuit and replaced with a fixed resistor (the big sand resistor). This would be confirmed by no change in resistance from pin 9 to ground when adjusting the Lin pot (not the big round one it sould be a little trim pot marked lin adj). So you would be stuck with what ever the lineaity is (no way to adj) which may be ok.
the big round pot looks like a height adj. you should see a 275 marked pin on the side of the board, I think I can make that out. But to be sure you can check the output from the filter choke, that is also 275v. see if the resistance is 0 at that 275 pin when comparing to the output side of the choke, then you know its the right one.
The 275v source is used in several of the pin resistance measurements (as well as ground of course).
again you dont want to make a lot of changes until after a base line run, I just ran into that when working on a color set. was working with a bit of snow, I pulled the chassis, cleaned the tuner, then checked tubes, replaced a couple out of spec parts and end up with no snow, but sync and color problems. turned out to be some of the new tubes as I put the old ones back in and problems went away. My hickok tube tester showed the old tubes as weak and the nos tubes as much better.
I would try to limit myself to just replacing the papers, and bad eletros, do a base line run to see where you are, then make one fix at a time.
Resistance and voltage measurements can be helpful but do not aways tell the whole problem.
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