[R-390] Tubes new or used?

[Bill Hawkins]

There's New Old Stock, which may be 40 years old.

IIRC, in one of our frequent ballast threads, it came out that
the iron resistor in a ballast tube is cooled by hydrogen. Now,
hydrogen, being the smallest atom, tends to escape from anything
made of bigger atoms, which is everything including glass.

So you need to be careful when you ask about "new" tubes. NOS
isn't necessarily what you're looking for.

Oh, and hydrogen makes iron brittle over time.

Just to kick over the can, unless you run your receivers from
poorly regulated field generators, you don't need a ballast tube.
And you don't need the heaters unless you alternate between
desert and polar regions with the same receiver. But if the set
was aligned with ovens on, it needs to be re-aligned with them off.
The calibrator oven needs to stay on.

Regards,
Bill Hawkins