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IIRC there were some poor condition phosphor patches (could have been caused by water dripping in) on the necked RACS tube...It was not ruined but it was not perfect either.
I still think a noble gas is better than a vacuum. You can probably get something heavier than helium for about the same price(making it cheaper than sourcing any usable vacuum pump and suitable accessories). Also consider that if you have a poor vacuum (not as good as factory) there WILL still be many corrosive air molecules inside...Make that trapped inside where they will continue to corrode the tube. Noble gas does not react with anything (anything includes metal, glass, cathode surface, and phosphor), and thus will not cause corrosion or degradation to the CRT. If the tube is stored face down, the gas is poured in through the neck, and the gas is heavier than the main constituent gasses in our atmosphere then the noble gas will sink to the bottom of the tube and slowly displace the air upwards and out through the neck. Think of this filling process like like filling the tube with water(don't fill your tube with water), the noble gas has a similar comparative density to air as does water so as you introduce noble gas gravity and negative buoyancy (relative to air) forces it to the bottom and it fills up the tube from the bottom as if you were pouring water in. If the leak is in the face the noble gas may slowly leak out (if the leak is only big enough for air molecules to pass through then heavier and thus larger noble gas molecules won't get through), but if the tube is face down a lot of gas would have to leak out before air could again reach the shadow mask and phosphors. The shadow mask and phosphors are the most critical part to preserve as they are the least replaceable, and permanent damage to them will affect the picture quality of a rebuild more than any other part that can be damaged by air.
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