12AX7 failure
 

Omer S wrote:

Why is it so important to debunk a failing tube that gave four years of
satisfactory performance?

Dude, just $#!^can the offending tube, and move on!

Its not *four years*, but only the ON-time in four years.

You living on some island where tubes grow on trees?

Regards,
H.

12AX7 failure
 

On Nov 27, 6:43*am, Heinz Schmitz wrote:
Omer S wrote:
Why is it so important to debunk a failing tube that gave four years of
satisfactory performance?

Dude, just $#!^can the offending tube, and move on!

Its not *four years*, but only the ON-time in four years.

You living on some island where tubes grow on trees?

Regards,
H.

Yikes!!

a) If the tube was Chinese, 6 weeks of "on-time" would be a lot in
some cases.
b) Current-production tubes are readily available. Not for free, and
one may vastly over-pay, but it is not as if it were a 19T8 or some-
such.
c) After determining that the equipment itself was not at fault, then
yes s&*t-can the tube and move on.

Peter Wieck
Melrose Park, PA

12AX7 failure
 

Heinz Schmitz wrote:

Omer S wrote:

Why is it so important to debunk a failing tube that gave four years of
satisfactory performance?

Dude, just $#!^can the offending tube, and move on!

Its not *four years*, but only the ON-time in four years.


So? Most tubes were only 90 day or one year warranty when they were
in full production. It wasn't uncommon to replace a failed tube, under
warranty. There are a lot of things that are involved in MTBF.


--
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There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you're crazy.

12AX7 failure
 

"Heinz Schmitz" wrote in message
...
Omer S wrote:

Why is it so important to debunk a failing tube that gave four years of
satisfactory performance?

Dude, just $#!^can the offending tube, and move on!

Its not *four years*, but only the ON-time in four years.

You living on some island where tubes grow on trees?

Regards,
H.


An interesting link, for further analysis of what could bring the demise of
12AX7 vacuum tubes,

Http://www.vaccuumtubefans.org/forums/Topic_12AX7

12AX7 failure
 

Omer S wrote in message
m...

"Heinz Schmitz" wrote in message
...
Omer S wrote:

Why is it so important to debunk a failing tube that gave four years of
satisfactory performance?

Dude, just $#!^can the offending tube, and move on!

Its not *four years*, but only the ON-time in four years.

You living on some island where tubes grow on trees?

Regards,
H.


An interesting link, for further analysis of what could bring the demise
of
12AX7 vacuum tubes,

Http://www.vaccuumtubefans.org/forums/Topic_12AX7






Could you check the URL
www.vaccuumtubefans.org/forums/Topic_12AX7

googling 1 c or cc or subdirectories, or similar domain got nowhere,
unusually. Nothing found via kloth.net domain whois


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

12AX7 failure
 

Michael A. Terrell wrote:

There are a lot of things that are involved in MTBF.

Yes, indeed.
But I guess that we are interested in those which we can influence.
Like e.g. (?)
- heating before applying anode voltage,
- avoiding long periods without anode current,
- ??

Regards,
H.

12AX7 failure
 

12AX7 failure
 

Heinz Schmitz wrote:

Michael A. Terrell wrote:

There are a lot of things that are involved in MTBF.

Yes, indeed.
But I guess that we are interested in those which we can influence.
Like e.g. (?)
- heating before applying anode voltage,
- avoiding long periods without anode current,


Useless on low power vacuum tubes that are not used in some bizarre
circuit. Its a different matter on high power transmitter tubes.

--
http://improve-usenet.org/index.html

aioe.org, Goggle Groups, and Web TV users must request to be white
listed, or I will not see your messages.

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm


There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you're crazy.

12AX7 failure
 

"N_Cook" wrote in message
...
Omer S wrote in message
m...



Could you check the URL
www.vaccuumtubefans.org/forums/Topic_12AX7


How about this link?

Http://www.vaccuumtubefans.org/forums/Topic_12AX7

12AX7 failure
 

Omer S wrote:

"N_Cook" wrote in message
...
Omer S wrote in message
m...



Could you check the URL
www.vaccuumtubefans.org/forums/Topic_12AX7


How about this link?

Http://www.vaccuumtubefans.org/forums/Topic_12AX7

Oh, Omer (Polly). What are we to think of you? Sigh.

-ex

12AX7 failure
 

Omer S wrote:

Http://www.vaccuumtubefans.org/forums/Topic_12AX7

nope, and networksolutions.com says that doesn't exist as a domain either.

Jeff

12AX7 failure
 

N_Cook wrote:
Omer S wrote in message
m...
"Heinz Schmitz" wrote in message
...
Omer S wrote:

Why is it so important to debunk a failing tube that gave four years of
satisfactory performance?

Dude, just $#!^can the offending tube, and move on!
Its not *four years*, but only the ON-time in four years.

You living on some island where tubes grow on trees?

Regards,
H.

An interesting link, for further analysis of what could bring the demise
of
12AX7 vacuum tubes,

Http://www.vaccuumtubefans.org/forums/Topic_12AX7






Could you check the URL
www.vaccuumtubefans.org/forums/Topic_12AX7


Same problem here.

I googled vaccuumtubefans and all I got was pointers back to this thread.

12AX7 failure
 

nobody wrote:
N_Cook wrote:
Omer S wrote in message
m...
"Heinz Schmitz" wrote in message
...
Omer S wrote:

Why is it so important to debunk a failing tube that gave four
years of
satisfactory performance?

Dude, just $#!^can the offending tube, and move on!
Its not *four years*, but only the ON-time in four years.

You living on some island where tubes grow on trees?

Regards,
H.

An interesting link, for further analysis of what could bring the demise
of
12AX7 vacuum tubes,

Http://www.vaccuumtubefans.org/forums/Topic_12AX7






Could you check the URL
www.vaccuumtubefans.org/forums/Topic_12AX7


Same problem here.

I googled vaccuumtubefans and all I got was pointers back to this thread.

The fellow who parroted and corrected another guy's link has a
reputation for not having verified his sources of info. Nuff said.

12AX7 failure
 

exray wrote:
The fellow who parroted and corrected another guy's link has a
reputation for not having verified his sources of info. Nuff said.

Back up and check the attributes Bill, The only one Omer is parroting
is himself.

Jeff

12AX7 failure
 

Michael A. Terrell wrote:

There are a lot of things that are involved in MTBF.

Yes, indeed.
But I guess that we are interested in those which we can influence.
Like e.g. (?)
- heating before applying anode voltage,
- avoiding long periods without anode current,

Useless on low power vacuum tubes that are not used in some bizarre
circuit. Its a different matter on high power transmitter tubes.

Your kind posting shares a property with many usenet postings:
It provokes the most valuable question: "Why?".

Regards,
H.

12AX7 failure
 

"N_Cook" wrote in message
...
Omer S wrote in message


Could you check the URL
www.vaccuumtubefans.org/forums/Topic_12AX7

googling 1 c or cc or subdirectories, or similar domain got nowhere,
unusually. Nothing found via kloth.net domain whois



Try this one!

http://tinyurl.com/4xur8r

Omer

12AX7 failure
 

Heinz Schmitz wrote:

Michael A. Terrell wrote:

There are a lot of things that are involved in MTBF.

Yes, indeed.
But I guess that we are interested in those which we can influence.
Like e.g. (?)
- heating before applying anode voltage,
- avoiding long periods without anode current,

Useless on low power vacuum tubes that are not used in some bizarre
circuit. Its a different matter on high power transmitter tubes.

Your kind posting shares a property with many usenet postings:
It provokes the most valuable question: "Why?".


Why, what? Have you ever seen any provable problems with low power
receiving tubes, or ar you just another tube freak repeating fairy tales
and folklore? Do you have decades of real experience with all types of
vacuum tubes behind you, or are you YAKIAH?


--
http://improve-usenet.org/index.html

aioe.org, Goggle Groups, and Web TV users must request to be white
listed, or I will not see your messages.

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm


There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you're crazy.

12AX7 failure
 

In article ,
Heinz Schmitz wrote:

Michael A. Terrell wrote:

There are a lot of things that are involved in MTBF.

Yes, indeed.
But I guess that we are interested in those which we can influence.
Like e.g. (?)
- heating before applying anode voltage,
- avoiding long periods without anode current,

Useless on low power vacuum tubes that are not used in some bizarre
circuit. Its a different matter on high power transmitter tubes.

Your kind posting shares a property with many usenet postings:
It provokes the most valuable question: "Why?".

So the real question is, is there anyone out there that can give a comprehensive
answer as to why?

Even the belief stated above that "Its a different matter on high power
transmitter tubes" with respect to "heating before applying anode voltage"
appears questionable.

Some 45 years ago I worked at several different stations as a broadcast engineer
and the old-timers there trained us young kids to be sure we thoroughly warmed
up the filaments before applying the plate power. The precise reasons for doing
this were never made completely clear. With the notable exception of one newly
installed RCA BTF-10D,the vast majority of the transmitters I worked with used
mercury vapor rectifiers, one even used two stacked banks of mercury vapor
rectifiers to provide the 17 kV B+ voltage. Obviously in transmitters using
mercury vapor rectifiers it is necessary to warm the rectifier filaments up
before applying power to the plate transformer(s), since dire things would
transpire if the mercury wasn't properly vaporized before the rectifiers where
hit with power from the plate transformer(s). But ignoring the mercury vapor
rectifiers was it really necessary to warm up the power tubes before applying
plate power? I was surprised a few years back to read in the instruction manual
for a tube transmitter the statement that it was not necessary to warm up the
power tube filaments before applying plate voltage! And they weren't just
saying that the automatic sequencer would take care of the correct sequencing of
the filament and plate power, the statement made clear that they were talking
about actually applying filament and plate power to the tube simultaneously. I
found this surprising since I had been trained to warm up the power tubes before
applying the plate voltage, and there are other reasons for warm up, so I asked
about this on a forum or newsgroup, the exact one has escaped me. A current
broadcast engineer replied and said yes that was true, it was generally not
necessary to warm up most power tube filaments before applying the plate
voltage. He did go on to explain that this was not universally the case however
and said there were certain types of tubes that did need to be warmed up first,
but I have forgotten what the reason was that he gave, probably something about
filament construction or material.

So does anyone have a comprehensive explanation of this cathode warm up issue,
for both low power and high power tubes?

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

12AX7 failure
 

Very funny ;o) At least I know how the taskman works! - JP


"Omer S" wrote in message
m...

"N_Cook" wrote in message
...
Omer S wrote in message


Could you check the URL
www.vaccuumtubefans.org/forums/Topic_12AX7

googling 1 c or cc or subdirectories, or similar domain got nowhere,
unusually. Nothing found via kloth.net domain whois



Try this one!

http://tinyurl.com/4xur8r

Omer

12AX7 failure
 

"Omer S" wrote in message
m...

"N_Cook" wrote in message
...
Omer S wrote in message


Could you check the URL
www.vaccuumtubefans.org/forums/Topic_12AX7

googling 1 c or cc or subdirectories, or similar domain got nowhere,
unusually. Nothing found via kloth.net domain whois



Try this one!

http://tinyurl.com/4xur8r

Omer

"JP" wrote in message
...
Very funny ;o) At least I know how the taskman works! - JP


Not funny! I didn't think of taskman, and had to shut down
the computer to get out of it.
Nelson

12AX7 failure
 

John Byrns wrote:

So does anyone have a comprehensive explanation of this cathode warm up issue,
for both low power and high power tubes?

My present understandig:
When the anode voltage is applied to the cold tube, the cathode during
heating up is operated in the saturation region. i.e. it cannot emit
as many electrons as could be drawn off.
It is said, that this can damage the cathode.

Why else would we find many devices where a relay does just that:
Switch on anode voltage only after the cathode is properly heated?
Just because of nice to have or to avoid start-up hum?

Regards,
H.

12AX7 failure
 

Michael A. Terrell wrote:

- heating before applying anode voltage,
- avoiding long periods without anode current,

Useless on low power vacuum tubes that are not used in some bizarre
circuit. Its a different matter on high power transmitter tubes.

Your kind posting shares a property with many usenet postings:
It provokes the most valuable question: "Why?".

Why, what? Have you ever seen any provable problems with low power
receiving tubes, or ar you just another tube freak repeating fairy tales
and folklore? Do you have decades of real experience with all types of
vacuum tubes behind you, or are you YAKIAH?

Is it not funny, that in many old tube radios you find ECH81, where
the triode part is deaf, whereas the heptode part still works fine?
One may assume, that the triode (oscillator for AM) was mainly
left without current, because people preferably listened to FM.

Why do tubes go?

Obviously what goes is the cathode. Obviously it does not burn,
like the wires in light bulbs. It loses the ability to emit. Now why
is that?

Regards,
H.

12AX7 failure
 

Tubes with pure tungsten filaments don't have to be preheated. They
don't have any coating or other material alloyed with it to damage.
Tungsten filament tubes can be run in emission-limited mode with no
problem; some are even made to be used this way. Examples are the 1236
and 2AS15. Tungsten filaments are also used in vacuum gauge tubes
because they aren't hurt by being exposed to air (when cold).

Pure tungsten filaments are used in very few tubes because they are
inefficient and have short life because of their high operating
temperature (they glow bright white).

Tubes that we are likely to encounter with pure tungsten filaments are
old ones like the 01. The inefficiency of these filaments can be seen
from the data sheets for these tubes. They take 5V at 1A whereas the
thoriated tungsten version, 01A, is 5V at 0.25A. Oxide coated filaments
are even more efficient; the 01B is 5V at 0.125A.

Heinz Schmitz wrote:
John Byrns wrote:

So does anyone have a comprehensive explanation of this cathode warm up issue,
for both low power and high power tubes?

My present understandig:
When the anode voltage is applied to the cold tube, the cathode during
heating up is operated in the saturation region. i.e. it cannot emit
as many electrons as could be drawn off.
It is said, that this can damage the cathode.

Why else would we find many devices where a relay does just that:
Switch on anode voltage only after the cathode is properly heated?
Just because of nice to have or to avoid start-up hum?

Regards,
H.




--
Jim Mueller

To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.