Re: Helium [was: t-bird screwing up]
On Tue 01 Nov 2022 at 06:49:09 (+0100), tomas@tuxteam.de wrote:
> On Mon, Oct 31, 2022 at 06:32:17PM -0400, gene heskett wrote:
>
> [...]
>
> > I think, but don't know for sure, that they were also helium filled drives,
> > a guaranteed disaster.
> >
> > They used the helium to make the heads fly lower, and when the helium leaked
> > out, and air leaked in,
>
> Possible.
>
> > the heads flew too high to read the disk. I don't know where Seagate
> > recruited the engineers who thought
> > up that idea,
> >
> > Whatever, even I with an 8th grade diploma, knows you cannot keep helium
> > anyplace for very long. Put it in a monel metal
> > bottle with walls an inch thick and its molecules's are so small that 10% of
> > it is gone in 6 or 7 hours.
So the He cylinders that we used after a few months in storage
really contained nothing at all!
> And these
> > jerks thought they could seal it up in a drive housing 1/16" thick?
The operative word is seal, not the thickness of the monel walls.
Seal—and no cracks.
> This is only a half-truth. You know what goes out faster than helium?
> Vacuum. And there was a whole glorious epoch in electronics which did
> rely on keeping vacuum "in". You should have some fond memories of
> that.
To be fair, most vacuum tubes aren't bathed in helium, but air, and
then only at a one atmosphere differential pressure. A gas cylinder
might be as high as 500 atmospheres.
And vacuum tubes do contain a getter to deal with outgassing, which
will help mitigate slight leaks.
Cheers,
David.
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