> I buy around 50 a year and many still have original
> 60's-70's date code
> tubes and put out full power. I dont think that you will
> ever see an
> Ameritron or Alpha running that long on original tubes;
> they push them a lot
> harder
That life part is true, but the reason you give is not.
The fact is today we cannot buy tubes that are anywhere near
as good or reliable as those made back in the 60's and 70's.
Around the late 80's it really all started falling apart. In
the mid to late 80's 8877's from Eimac were nearly all bad
brand new (tube failures in MRI equipment nearly put ETO out
of business) and Richardson's swallowed up Cetron and the
rest.
When Ameritron started producing the AL-572B they made a
mass purchase of Svetlana 572B's, and the majority of new
tubes were bad (and old) right off the shelf. The only
alternative, largely due to Richardson's swallowing up all
the manufacturing and pricing 572's out of reach, were
Chinese tubes. The Chinese tubes were tested only at 1500
volts or so and a few hundred watts, and the glass and other
materials were far substandard to the old Cetron's.
I can take 35 year old Cetrons that have been sitting up on
a shelf and the majority high-pot to 8 or 9 kV, but about
50% of brand new Chinese 572B tubes fail at 5kV or less.
The real truth is no matter how you run most modern tubes,
the life on average won't be anywhere near the life of tubes
before all the people who knew what they were doing retired
or got fired.
The problem doesn't stop at the food supply, anything that
requires extraordinary care (like tubes) isn't as good as it
was. That's the real reason.
73 Tom
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