Spyke
lemmy.ca

How much pressure? Is the bulb pressurized or the smaller tube? Is it normal air or something specific like nitrogen?

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I searched it up:

It seems the smaller tube is pressurised, the larger bulb is under a vacuum. Some of the other diagrams also show a getter in the bulb, so it's a proper vacuum tube level vacuum.

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This is what the insides of a high pressure sodium (HPS) light bulb look like | Spyke