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Patrick Turner
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Jon Yaeger
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flipper
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 Posted:
Thu Sep 15, 2005 5:56 pm Post subject:
Re: 5881 an interesting read from 1950. |
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On Thu, 15 Sep 2005 11:21:38 GMT, Patrick Turner
<info@turneraudio.com.au> wrote:
Good read. |
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Patrick Turner
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| Posted:
Thu Sep 15, 2005 9:54 pm Post subject:
Re: 5881 an interesting read from 1950. |
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flipper wrote:
The article tell ppl about a number of problems one can get with tubes,
not just
5881 etc.
Gold plated grid wires and special screen coatings and fancy anode
materials improve tubes a lot.
The countries that make tubes without all these techniques cannot claim
to be making premium grade tubes.
Patrick Turner. |
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flipper
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| Posted:
Thu Sep 15, 2005 11:07 pm Post subject:
Re: 5881 an interesting read from 1950. |
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On Thu, 15 Sep 2005 16:54:29 GMT, Patrick Turner
<info@turneraudio.com.au> wrote:
You betcha and that's what I meant.
I wish he'd gone a bit more into the actual mechanism behind 'sleeping
sickness' though.
| Quote: | Gold plated grid wires and special screen coatings and fancy anode
materials improve tubes a lot.
The countries that make tubes without all these techniques cannot claim
to be making premium grade tubes.
Patrick Turner.
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Patrick Turner
Guest
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| Posted:
Fri Sep 16, 2005 11:41 am Post subject:
Re: 5881 an interesting read from 1950. |
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flipper wrote:
| Quote: | On Thu, 15 Sep 2005 16:54:29 GMT, Patrick Turner
info@turneraudio.com.au> wrote:
flipper wrote:
On Thu, 15 Sep 2005 11:21:38 GMT, Patrick Turner
info@turneraudio.com.au> wrote:
Dudes, try going to http://www.fust-electronica.nl/5881.htm
Patrick Turner.
Good read.
The article tell ppl about a number of problems one can get with tubes,
not just
5881 etc.
You betcha and that's what I meant.
I wish he'd gone a bit more into the actual mechanism behind 'sleeping
sickness' though.
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Never put tubes to bed in a dark room.
That way they won't fall asleep :-)
Patrick Turner.
| Quote: |
Gold plated grid wires and special screen coatings and fancy anode
materials improve tubes a lot.
The countries that make tubes without all these techniques cannot claim
to be making premium grade tubes.
Patrick Turner.
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flipper
Guest
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| Posted:
Fri Sep 16, 2005 11:51 am Post subject:
Re: 5881 an interesting read from 1950. |
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On Fri, 16 Sep 2005 06:41:54 GMT, Patrick Turner
<info@turneraudio.com.au> wrote:
| Quote: |
flipper wrote:
On Thu, 15 Sep 2005 16:54:29 GMT, Patrick Turner
info@turneraudio.com.au> wrote:
flipper wrote:
On Thu, 15 Sep 2005 11:21:38 GMT, Patrick Turner
info@turneraudio.com.au> wrote:
Dudes, try going to http://www.fust-electronica.nl/5881.htm
Patrick Turner.
Good read.
The article tell ppl about a number of problems one can get with tubes,
not just
5881 etc.
You betcha and that's what I meant.
I wish he'd gone a bit more into the actual mechanism behind 'sleeping
sickness' though.
Never put tubes to bed in a dark room.
That way they won't fall asleep :-)
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LOL. Ok, I'll remember that and leave the filaments glowing ;)
Oh wait, that's what causes it to begin with.
I found it interesting because it seems to be a bit contradictory to
the cathode stripping crowd.
| Quote: | Patrick Turner.
Gold plated grid wires and special screen coatings and fancy anode
materials improve tubes a lot.
The countries that make tubes without all these techniques cannot claim
to be making premium grade tubes.
Patrick Turner.
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Ruud Broens
Guest
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| Posted:
Sun Sep 18, 2005 2:31 am Post subject:
Re: 5881 an interesting read from 1950. |
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"flipper" <flipper@fish.net> wrote in message
news:jjqki15j05nvv76bslct6ljo4bsd7kkbit@4ax.com...
: On Fri, 16 Sep 2005 06:41:54 GMT, Patrick Turner
: <info@turneraudio.com.au> wrote:
:
: LOL. Ok, I'll remember that and leave the filaments glowing ;)
:
: Oh wait, that's what causes it to begin with.
:
: I found it interesting because it seems to be a bit contradictory to
: the cathode stripping crowd.
Well, to put things in perspective, c.s. is not some imaginary
boutique-speak, but rather a well researched phenomenon.
Not by some internet wannabe skeptic (as in the article you
mentioned elsewhere ~reasoning~ from rectifier tubes) but
by physicists holding phd's with scientific and commercial
interest in the matter - the research & development guys
that were responsible for the production of millions of tubes
now some half a century ago.
Whether or not one should worry about it, is another matter.
I think Fabio has given the common sense approach, when using
expensive tubes , better safe than sorry :-)
In general, avoiding overstressing electrical or mechanical
components is always good practice.
BTW, the 5881 article gives one reason why a tube with grid(s)
gives a lot more potential problems with 'cathode dust' than a
rectifier - you don't want a grid as an emission source !
Rudy |
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flipper
Guest
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| Posted:
Sun Sep 18, 2005 10:06 am Post subject:
Re: 5881 an interesting read from 1950. |
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On Sat, 17 Sep 2005 23:31:23 +0200, "Ruud Broens" <broensr@wanadoo.nl>
wrote:
| Quote: |
"flipper" <flipper@fish.net> wrote in message
news:jjqki15j05nvv76bslct6ljo4bsd7kkbit@4ax.com...
: On Fri, 16 Sep 2005 06:41:54 GMT, Patrick Turner
: <info@turneraudio.com.au> wrote:
:
: LOL. Ok, I'll remember that and leave the filaments glowing ;)
:
: Oh wait, that's what causes it to begin with.
:
: I found it interesting because it seems to be a bit contradictory to
: the cathode stripping crowd.
Well, to put things in perspective, c.s. is not some imaginary
boutique-speak, but rather a well researched phenomenon.
Not by some internet wannabe skeptic (as in the article you
mentioned elsewhere ~reasoning~ from rectifier tubes) but
by physicists holding phd's with scientific and commercial
interest in the matter - the research & development guys
that were responsible for the production of millions of tubes
now some half a century ago.
|
I think you mischaracterized the person's reasoning but I'd love to
see something by the experts you mention if you'd point me to one.
| Quote: |
Whether or not one should worry about it, is another matter.
I think Fabio has given the common sense approach, when using
expensive tubes , better safe than sorry :-)
In general, avoiding overstressing electrical or mechanical
components is always good practice.
BTW, the 5881 article gives one reason why a tube with grid(s)
gives a lot more potential problems with 'cathode dust' than a
rectifier - you don't want a grid as an emission source !
Rudy
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Ruud Broens
Guest
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| Posted:
Sun Sep 18, 2005 8:56 pm Post subject:
Re: 5881 an interesting read from 1950. |
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"flipper" <flipper@fish.net> wrote in message
news:natpi1lk4bl131c2e1us2ajc2fp55i4kt3@4ax.com...
: On Sat, 17 Sep 2005 23:31:23 +0200, "Ruud Broens" <broensr@wanadoo.nl>
: wrote:
:
: >
: >"flipper" <flipper@fish.net> wrote in message
: >news:jjqki15j05nvv76bslct6ljo4bsd7kkbit@4ax.com...
: >: On Fri, 16 Sep 2005 06:41:54 GMT, Patrick Turner
: >: <info@turneraudio.com.au> wrote:
: >:
: >: LOL. Ok, I'll remember that and leave the filaments glowing ;)
: >:
: >: Oh wait, that's what causes it to begin with.
: >:
: >: I found it interesting because it seems to be a bit contradictory to
: >: the cathode stripping crowd.
: >
: >Well, to put things in perspective, c.s. is not some imaginary
: >boutique-speak, but rather a well researched phenomenon.
: >Not by some internet wannabe skeptic (as in the article you
: >mentioned elsewhere ~reasoning~ from rectifier tubes) but
: >by physicists holding phd's with scientific and commercial
: >interest in the matter - the research & development guys
: >that were responsible for the production of millions of tubes
: >now some half a century ago.
:
: I think you mischaracterized the person's reasoning but I'd love to
: see something by the experts you mention if you'd point me to one.
Heh, ok, googling "sputtering" with this NG will get you some earlier
info i posted; here a snippet from a Philips Tech. Library book, 1964:
"The main causes of deterioration of the cathode are evaporation and
sputtering. A well-designed coated cathode will give very slight
evaporation and sputtering, as long as the current remains below
the saturation current. If the tube is operated under suitable conditions,
both these causes of deterioration can be neglected."
- sputtering being the term for cathode stripping as used in the industry.
So far, so good. But of course, what are the less-than-suitable conditions ?
A graph shows the saturation current density for a BaO/SrO coating
as a function of the true temperature in K of the cathode (and those for
tungsten/thoriated tungsten type tubes). Over a million A/m^2 at 1300 K
or above should not be exeeded or sputtering will take place - not exactly
a problem :-)
At 500 K, however, this has fallen dramatically: a 100 mA per square meter
of cathode will get you into trouble !
For a few seconds during heating up from room temperature, if B+ is
present, the cathode will be exposed to current exeeding the saturation current.
Once above say 800K, no worries, you'll never get anywhere near problematic
current - well, maybe with power tubes operated well above their 'guidelines' :-)
Cheers,
Rudy
: >
: >Whether or not one should worry about it, is another matter.
: >I think Fabio has given the common sense approach, when using
: >expensive tubes , better safe than sorry :-)
: >In general, avoiding overstressing electrical or mechanical
: >components is always good practice.
: >
: >BTW, the 5881 article gives one reason why a tube with grid(s)
: >gives a lot more potential problems with 'cathode dust' than a
: >rectifier - you don't want a grid as an emission source !
: >
: >Rudy
: >
: |
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Joseph Meditz
Guest
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| Posted:
Sun Sep 18, 2005 11:55 pm Post subject:
Re: 5881 an interesting read from 1950. |
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| Quote: | A graph shows the saturation current density for a BaO/SrO coating
as a function of the true temperature in K of the cathode (and those for
tungsten/thoriated tungsten type tubes). Over a million A/m^2 at 1300 K
or above should not be exeeded or sputtering will take place - not exactly
a problem :-)
At 500 K, however, this has fallen dramatically: a 100 mA per square meter
of cathode will get you into trouble !
For a few seconds during heating up from room temperature, if B+ is
present, the cathode will be exposed to current exeeding the saturation current.
|
At what B+ voltage does this happen? Surely the value of B+ must be a
factor.
| Quote: | Once above say 800K, no worries, you'll never get anywhere near problematic
current - well, maybe with power tubes operated well above their 'guidelines' :-)
|
The question of cathode stripping was raised in AGA a while ago. The
OP's question was whether this is a problem for tubes operated at a few
hundred volts in audio circuits. He surmized that this issue was
mainly of concern in high voltage transmitters. The OP said he ignored
the standby SW in his guitar amp and did not notice premature tube
wear.
Best regards,
Joe |
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Sander deWaal
Guest
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| Posted:
Mon Sep 19, 2005 2:07 am Post subject:
Re: 5881 an interesting read from 1950. |
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"Joseph Meditz" <josephmeditz@yahoo.com> said:
| Quote: | The question of cathode stripping was raised in AGA a while ago. The
OP's question was whether this is a problem for tubes operated at a few
hundred volts in audio circuits. He surmized that this issue was
mainly of concern in high voltage transmitters. The OP said he ignored
the standby SW in his guitar amp and did not notice premature tube
wear.
|
That's probably because in most guitar amps, the power tubes are
abused so hard that their useful life is short enough not to encounter
any problems due to cathode stripping or even cathode poisoning.
OTOH, how do we know that an exhausted set of tubes *didn't* suffer
from beforementioned problems? :-)
--
"Audio as a serious hobby is going down the tubes."
- Howard Ferstler, 25/4/2005 |
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Ruud Broens
Guest
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| Posted:
Mon Sep 19, 2005 7:08 pm Post subject:
Re: 5881 an interesting read from 1950. |
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"Sander deWaal" <nospam@wanadoo.nl> wrote in message
news:gjlri19pvmass0ecqgijathb7gf3csaekl@4ax.com...
: "Joseph Meditz" <josephmeditz@yahoo.com> said:
:
: >The question of cathode stripping was raised in AGA a while ago. The
: >OP's question was whether this is a problem for tubes operated at a few
: >hundred volts in audio circuits. He surmized that this issue was
: >mainly of concern in high voltage transmitters. The OP said he ignored
: >the standby SW in his guitar amp and did not notice premature tube
: >wear.
:
:
: That's probably because in most guitar amps, the power tubes are
: abused so hard that their useful life is short enough not to encounter
: any problems due to cathode stripping or even cathode poisoning.
:
: OTOH, how do we know that an exhausted set of tubes *didn't* suffer
: from beforementioned problems? :-)
:
: --
:
: "Audio as a serious hobby is going down the tubes."
: - Howard Ferstler, 25/4/2005
Darn, that's exactly what i was going to post, you beat me to it,
again :-), Sander.
How much the usefull lifetime of a tube is reduced by the start-up
strippin ? No data on that, Joseph, or at least i've not come across that.
My guestimate: anywhere between 0 and 15 %. No biggie unless it
happens to be a rare tube. And an increase in the change of catastrophic
failure, in case the material lost from the cathode finds it way to the
worst places - Murphy's law makes that something to think about :-)
Some of my conclusions:
- an SS rectifier & slow turn-on filament heating is the worst combination,
aggravating the effect by prolonging the low-temp cathode phase
- the effect must be a lot more significant for power tubes than for
pre-amp / driver tubes
- an alternative to delayed B+ circuitry may be to use filament heating
during start-up in a way to minimize the relatively cold cathode phase
Rudy
btw Sander, heb je al zo'n i Love 180 km/u sticker ? ;-) |
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Eike Lantzsch, ZP6CGE
Guest
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| Posted:
Mon Sep 19, 2005 9:17 pm Post subject:
Re: 5881 an interesting read from 1950. |
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Ruud Broens wrote:
| Quote: |
"Sander deWaal" <nospam@wanadoo.nl> wrote in message
news:gjlri19pvmass0ecqgijathb7gf3csaekl@4ax.com...
: "Joseph Meditz" <josephmeditz@yahoo.com> said:
:
: >The question of cathode stripping was raised in AGA a while ago. The
: >OP's question was whether this is a problem for tubes operated at a few
: >hundred volts in audio circuits. He surmized that this issue was
: >mainly of concern in high voltage transmitters. The OP said he ignored
: >the standby SW in his guitar amp and did not notice premature tube
: >wear.
:
:
: That's probably because in most guitar amps, the power tubes are
: abused so hard that their useful life is short enough not to encounter
: any problems due to cathode stripping or even cathode poisoning.
:
: OTOH, how do we know that an exhausted set of tubes *didn't* suffer
: from beforementioned problems? :-)
:
: --
:
: "Audio as a serious hobby is going down the tubes."
: - Howard Ferstler, 25/4/2005
Darn, that's exactly what i was going to post, you beat me to it,
again :-), Sander.
How much the usefull lifetime of a tube is reduced by the start-up
strippin ? No data on that, Joseph, or at least i've not come across that.
My guestimate: anywhere between 0 and 15 %. No biggie unless it
happens to be a rare tube. And an increase in the change of catastrophic
failure, in case the material lost from the cathode finds it way to the
worst places - Murphy's law makes that something to think about :-)
Some of my conclusions:
- an SS rectifier & slow turn-on filament heating is the worst combination,
aggravating the effect by prolonging the low-temp cathode phase
- the effect must be a lot more significant for power tubes than for
pre-amp / driver tubes
- an alternative to delayed B+ circuitry may be to use filament heating
during start-up in a way to minimize the relatively cold cathode phase
Rudy
|
I was asking myself if some of those european tubes, like PCL805, have
the bright heater glow on startup to avoid cathode stripping?
Is anybody wise to this?
Kind regards, Eike
-- |
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Sander deWaal
Guest
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| Posted:
Mon Sep 19, 2005 10:08 pm Post subject:
Re: 5881 an interesting read from 1950. |
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"Ruud Broens" <broensr@wanadoo.nl> said:
| Quote: | btw Sander, heb je al zo'n i Love 180 km/u sticker ? ;-)
|
Neuh, ik plak geen stikkers, ik *rijd* gewoon 180 :-))))
--
"Audio as a serious hobby is going down the tubes."
- Howard Ferstler, 25/4/2005 |
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