Topics

Morning fun - working scope with no tubes?

Jamie Ostrowski
 

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
testers.

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.


Chuck Harris
 

In some uses, the tube type was pretty important.
Heathkit was forever banning this brand, or that from
use in their amateur radio equipment. This was because
there were subtle differences in inter-electrode capacitances,
and gain curves between the different maker's same numbered
tubes. A GE 12AX7 might not work, but an Amperex might. It
was also because they were working the tubes pretty hard.

Audio amplifiers work their tubes pretty hard too, and often
have been cheapened in ways that make them rely on the quirky
characteristics of certain brands of tubes. Only certain
makers of 6V6's would sound right in the old Fender amplifiers.
And, that was in the 50's and 60's.. tube's hay day. Most of
the newer Russian copies won't work right with the simple biasing
methods Fender used. They don't distort right at the right
setting of the volume controls.

Remember, the different makers did not get their tube designs
from the originator of the tube type. They designed their
own to match the original maker's specs, and to work well with
their manufacturing capabilities. Some were better than others.

Many brands actually bought their tubes from other vendors. For
instance Silvertone never made a single vacuum tube, and yet they
sold millions under their brand

I think there were fewer than a dozen tube manufacturers in the
peak of tube usage. And those that were there often filled out
their line by buying from other makers.

-Chuck Harris

Jamie Ostrowski wrote:

Yes I think that is a good question.

I asked a similar question about a month ago to this group if I needed to
be concerned about whether the say, 12AX7 with the special D getter, black
plate, et al 12AX7's being sold on ebay were equal to a standard GE 12AX7
in one of my oscilloscopes, and the answer I got from some of the brightest
minds here was that there was no difference. I could use any 12AX7.
(Granted I would stay away from the Chinese stuff).

We could probably be sure of the answer to that if we knew what brand of
tubes were used in these scopes when they were manufactured. If the answer
was GE, RCA, Sylvania tubes, then we would know right away that there could
be no negative impact.

But most of these scopes have had their tubes replaced throughout the
years. I don't know what tube brands were originally installed.

Chuck Harris
 

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
testers.

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.




Jamie Ostrowski
 

Thanks for all the info, Chuck. Very informative.

On Fri, Sep 20, 2019 at 5:17 PM Chuck Harris <cfharris@...> wrote:

In some uses, the tube type was pretty important.
Heathkit was forever banning this brand, or that from
use in their amateur radio equipment. This was because
there were subtle differences in inter-electrode capacitances,
and gain curves between the different maker's same numbered
tubes. A GE 12AX7 might not work, but an Amperex might. It
was also because they were working the tubes pretty hard.

Audio amplifiers work their tubes pretty hard too, and often
have been cheapened in ways that make them rely on the quirky
characteristics of certain brands of tubes. Only certain
makers of 6V6's would sound right in the old Fender amplifiers.
And, that was in the 50's and 60's.. tube's hay day. Most of
the newer Russian copies won't work right with the simple biasing
methods Fender used. They don't distort right at the right
setting of the volume controls.

Remember, the different makers did not get their tube designs
from the originator of the tube type. They designed their
own to match the original maker's specs, and to work well with
their manufacturing capabilities. Some were better than others.

Many brands actually bought their tubes from other vendors. For
instance Silvertone never made a single vacuum tube, and yet they
sold millions under their brand

I think there were fewer than a dozen tube manufacturers in the
peak of tube usage. And those that were there often filled out
their line by buying from other makers.

-Chuck Harris

Jamie Ostrowski wrote:
Yes I think that is a good question.

I asked a similar question about a month ago to this group if I needed to
be concerned about whether the say, 12AX7 with the special D getter,
black
plate, et al 12AX7's being sold on ebay were equal to a standard GE 12AX7
in one of my oscilloscopes, and the answer I got from some of the
brightest
minds here was that there was no difference. I could use any 12AX7.
(Granted I would stay away from the Chinese stuff).

We could probably be sure of the answer to that if we knew what brand of
tubes were used in these scopes when they were manufactured. If the
answer
was GE, RCA, Sylvania tubes, then we would know right away that there
could
be no negative impact.

But most of these scopes have had their tubes replaced throughout the
years. I don't know what tube brands were originally installed.



Mlynch001
 

Chuck,

As always, I enjoy all information that you bring out in your posts.

Thanks!

--
Michael Lynch
Dardanelle, AR

 

Yes,
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,

Robin

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
testers.

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.





 

An old saw comes to mind here. Did you know the word gullible is not in the dictionary?

Regards

On 9/20/2019 6:05 PM, 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
testers.

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.


 

Hi Tom,
I just checked on-line dictionaries from Merriam-Webster, Webster's Online Dictionary, Cambridge English Dictionary, Collins English Dictionary, and on and on. They all provide definitions for it.

Uh Oh! Did I fall for your trick and prove your point because I was gullible enough to challenge your claim? :)

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Tom Miller
Sent: Friday, September 20, 2019 5:40 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Morning fun - working scope with no tubes?

An old saw comes to mind here. Did you know the word gullible is not in the dictionary?

Regards




--
Dennis Tillman W7PF
TekScopes Moderator

 

Hi Robin,
You are referring to the Long Tail Pair which is an incredibly versatile circuit that has been used for over 80 years n tube circuits, transistor circuits, and integrated circuits.

Wikipedia includes the historical background of this circuit in their article on Differential Amplifiers (the Long tail Pair is a simple differential amplifier):
https://en.wikipedia.org/wiki/Differential_amplifier

An explanation of how the vacuum tube Long Tail Pair works is given at
http://www.valvewizard.co.uk/dcltp.html

Fender (and many others) used the Long Tail Pair as a phase inverter in their guitar amplifiers:
https://www.tdpri.com/threads/how-the-long-tail-pair-phase-inverter-works.519077/

Although the Long Tail Pair circuit was originally developed for vacuum tube amplifiers it is so general it works as well for transistors. This article describes how the transistor version works and how it is used extensively in IC OpAmps and Differential Comparators:
https://www.electronics-notes.com/articles/analogue_circuits/transistor/long-tailed-pair-circuit.php

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Robin_Birch
Sent: Friday, September 20, 2019 3:44 PM

Yes,
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,.



--
Dennis Tillman W7PF
TekScopes Moderator