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Old 2nd March 2013, 11:00 PM   #21
Magz is offline Magz  United States
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Quote:
Originally Posted by Harleyjon View Post
If you take a look at the link supplied, it clearly states that the absolute vacumm is attained by an explosion within the valve using the getter to spray a Barium compound. Hence the mirrored effect on the inside of the envelope.

This action is a once only action and it caused electrically, without using heat!

http://www.vacuumstate.com/fileuploa...lves%20pix.pdf

Getter flashing is caused by electrically or inductively heating the getter ring. The getter material deposited on the glass will react with any stray gases in the tube, but at room temperature that reaction will be many times slower than it was during the flashing process.

Chemical reactions such as the getter absorbing stray gases are temperature dependent (google Arrhenius if you want to know more). Roughly, every 10degC decrease in temperature halves the reaction rate.

All tubes have some very small level of leakage, which can result in significant amounts of gas diffusing into the partial vacuum of the tube envelope over the course of many decades; a 1920s vintage balloon tube like a 26, for example, may have been stored in an often cold warehouse for almost 90 years! At low temperatures, the reaction rate of the barium getter with the gas will be slowed considerably, and may actually be slower than the rate of gas ingression into the tube, hence residual gas levels will increase.

So, a heat treatment prior to use may in fact be a reasonable prophylactic measure, provided you do not melt the tube base via overzealousness.
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Old 2nd March 2013, 11:10 PM   #22
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Quote:
Originally Posted by Harleyjon View Post
Meltdown comes to mind here but an interesting concept.
I think, after over 50 years of valve gear repairing, that there is more than a jot of evidence that running the valves for a minute or so before putting power on the anodes keeps the cathodes in good condition and maximizes the life of the valve. (6L6, EL34, 2A3, KT88 etc). So maybe warming them up first will help.
I like heat the cathode for least 20 minutes, after it + 20 minutes with the HV(without music), and the tube are ready to do some music.

Michael Boele 6C33 datasheet say the minimum heat time(90% emission) for this tube in military use is 120 seconds, where it is grant for 1000 hours only.

But tubes vendors will disagree, as they want sell more tubes to the custumer, as early as possible.
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Old 3rd March 2013, 12:07 AM   #23
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Just noting a few things...

Seems to me that this is a lot of work for something that ought to happen when you start up the heaters or even run the tubes initially (and not baking means the bakelite bases stay nice looking). Maybe I haven't got such expensive tubes to try this on or the ones that I do have just aren't worth the effort.

But inherently knowing that this is a very short lived component (I have been told that useful life can be measured in the thousands of hours), I am not sure that I would want to even bother as I get my inspiration from people like George at tubelab. If there was a way I would want to push a tube to maximize performance, I would go with George's awesome methodology on pushing a tube.

I also have a feeling that those Solid State Class A guys must be reading some of these posts and scratching their heads wondering what all the fuss is about.
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Old 3rd March 2013, 12:22 AM   #24
TheGimp is offline TheGimp  United States
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Quote:
Originally Posted by Tony View Post
anyone tried induction heating using coils wrapped around the tube?
Thought about it. Looked up designs for induction heaters but never bothered to try.

Popped a couple in a microwave.

Don't bother.
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Old 3rd March 2013, 12:39 AM   #25
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Originally Posted by overtheairbroadcast View Post
Just noting a few things...

Seems to me that this is a lot of work for something that ought to happen when you start up the heaters or even run the tubes initially (and not baking means the bakelite bases stay nice looking). Maybe I haven't got such expensive tubes to try this on or the ones that I do have just aren't worth the effort.

But inherently knowing that this is a very short lived component (I have been told that useful life can be measured in the thousands of hours), I am not sure that I would want to even bother as I get my inspiration from people like George at tubelab. If there was a way I would want to push a tube to maximize performance, I would go with George's awesome methodology on pushing a tube.

I also have a feeling that those Solid State Class A guys must be reading some of these posts and scratching their heads wondering what all the fuss is about.
I afraid activate the getter and degassing a NOS tube is not this fast, it is a slow process to some hours or days if one had a 6V eletrical heater for the cathode.

Powering any cold tube with the high voltage B+ always implies a dramatic reduction in the useful life of the valve.

Iam pretty sure run an tube amp as a test tube device is a dangerous situation, as a new tube may damaged the amp or even made a fire.
Insert a untested new tube in a amp is a risky act.

My tubes dont had baquelite base, 6C33 usually run over 200ļC in regular use, so baking is not a prob.
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Last edited by FullRangeMan; 3rd March 2013 at 12:48 AM.
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Old 3rd March 2013, 02:41 AM   #26
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I just don't get it...first you want to freeze em with super-cold cryrogenics ....now you want to "bake" them. Make up your mind here, how about we split the difference and keep them at (Gasp)..room temperature.


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Old 3rd March 2013, 02:53 AM   #27
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Originally Posted by Richard Ellis View Post
I just don't get it...first you want to freeze em with super-cold cryrogenics ....now you want to "bake" them. Make up your mind here, how about we split the difference and keep them at (Gasp)..room temperature.


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I dont want cryogenics anything, I nor even talk on it.
I am ask info on baking tubes.
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Old 3rd March 2013, 03:18 AM   #28
AJT is offline AJT  Philippines
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Quote:
Originally Posted by TheGimp View Post
Thought about it. Looked up designs for induction heaters but never bothered to try.

Popped a couple in a microwave.

Don't bother.
the best thing to do then is to just get a tube that you need not bake in the oven, too much trouble for so little gain...
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Old 3rd March 2013, 04:32 AM   #29
Magz is offline Magz  United States
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Originally Posted by TheGimp View Post
Thought about it. Looked up designs for induction heaters but never bothered to try.

Popped a couple in a microwave.

Don't bother.
Induction works initially because the getter ring forms a shorted antenna to the RF energy. Since the barium getter is in the ring, it gets ballistically heated. Repeating the inductive heating after the fact will still heat the ring, but the barium is now on the glass, so any effect would most likely be negligible, IMO.
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Old 3rd March 2013, 08:35 AM   #30
Merlinb is offline Merlinb  United Kingdom
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Originally Posted by overtheairbroadcast View Post
Being as closed minded and ignorant as I am, I can not see what this would achieve even with the premise of activating the getter by heating it to get rid of residual gases.

At 175 C for three hours is more like cooking an unstuffed turkey, but wouldn't that already be surpassed by just turning on your amp and powering up the tube and heaters and playing music through it for a good while?
The theory is that you want the residual gas to be soaked up by the getter without having to heat the cathode to a normal working temperature, and without drawing any current. Residual gas can attack the cathode, but this effect is greatest when the cathode is fully heated. If you simply switch on an old valve and use it for a while, it is possible that you are ionising the gas and allowing it to attack the cathode before the getter has had much chance to do anything. In the oven, however, you can heat everything to a couple of hundred degrees (normal working temp) so the getter can do its job, but the cathode is no hotter than anything else.

Whether it is truly an effective treatment, I don't know.

Quote:
Powering any cold tube with the high voltage B+ always implies a dramatic reduction in the useful life of the valve.
There is no real evidence to support this.

Last edited by Merlinb; 3rd March 2013 at 08:38 AM.
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