Re: Morning fun - working scope with no tubes?


Designing stuff so that it was, as much as possible, independent of the particular characteristics of a given device as it aged or cane from various suppliers, was one of the great skills of tube design,


On 20 Sep 2019, at 23:22, Chuck Harris <cfharris@...> wrote:

I think BB's were, as well as most any other high quality
brand. Tektronix made scopes, not radio tubes. They
tested what they sold, and designed their circuits so that
they generally were not too dependent on the exact characteristics
of the different tubes.

Bugle Boys were just ordinary tubes that you might find at
your local drugstore, or TV repair store.

-Chuck Harris

Jamie Ostrowski wrote:
Chuck, do you know if the Bugle Boy, etc, tubes were even used in the
original builds, or what brand they used originally?

On Fri, Sep 20, 2019 at 5:00 PM Chuck Harris <cfharris@...> wrote:

That is something that few people understand.

Tektronix was trying to get state of the art performance
out of fairly common vacuum tubes..... but with as long
a vacuum tube life as they could reasonably manage. There
were a lot of tubes in these scopes. If reliability was
compromised, probability is you would be replacing a tube
every few months... sort of like the old color TV's...

This required them to use configurations that had cathode
bias to very high negative voltages, to keep the currents
effectively constant, and to use each stage with fairly low
gain, making the gain up over multiple stages. Linearity
was very important to tektronix engineers.

By the time a tektronix scope tube is starting to show a
noticeable reduction in performance in a tektronix scope,
it is dead, dead, dead... for the more basic circuits used
in tube testers, and audio amplifiers. And has been for
quite a while.

This is why tektronix stated in most all of their manuals
that the best tester for the tubes in your scope, was the
scope itself. They didn't believe very highly in tube

So, many of those spiffy bugle-boy tubes, that work just fine
in a scope, have had just about every last drop of goodness
extracted from them... And, will test bad in your fancy
Hickok tester.

Just a thought.

-Chuck Harris

Mlynch001 wrote:
I don’t have a dog in the hunt here, as I buying and fixing later model
solid state TEK scopes and other gear. It seems to me that a scope that
will function correctly at the frequencies that we request of them must be
just as demanding of the tubes? If all of this audiophool nonsense is
true, none of our scopes is worth a darn. I don’t have a $2500 power
cord, $150 receptacle, cryogenic treated breakers or wire. How does my
scope function and deliver usable results? Crap in . . . Crap out! Just
thinking out loud.

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