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Old 6th March 2013, 11:42 PM   #101
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After reading the pdf I was a bit disappointed about the lack of scientific content. In the text the only reference to another publication is to a book of the author himself.
Furthermore, where are the statistics that there is actually a problem that needs solving?
If, over several decades some gas has found its way into the internals of a valve, that gas can only be air: 20% oxigen, 79% nitrogen and 1% argon. A barium getter will quickly react with the oxigen, but it does nothing with the other gasses. So, if the problem is gas coming from outside, even 'reactivating' the barium getter still leaves 80% of the problem. Big deal.

In his own collection of two types of small signal valves he found improvement after baking the problem valves. What would have happened to those if they would just have been used in a real circuit? Is cathode poisoning in these cases a likely danger? Give me numbers: what percentage of valves die because of this? How much shorter valve life? Differences between small signal, power and transmitting types?

I'm not saying that the problem the author describes is not real, because I do not know. All I know is that I just plug in old valves and most of them just work perfectly.
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Old 6th March 2013, 11:50 PM   #102
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Valves can last a very long time.
A TV and Radio engineer gave me a 1940's valve amplifier from a radio for my electric guitar. It blew a couple of capacitors on power up but after replacing the capacitors the valves burst into life and sounded very good.

I suspect air entering valves is a rare problem and not worth worrying about.
If someone is mistreating valves like banging them around then they deserve any problems they get.
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Old 7th March 2013, 12:38 AM   #103
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Quote:
Originally Posted by wicked1 View Post
after watching that, some Mullard Blackburn video's from the 50's or 60's showed up, and they were incredible!! They NEVER touched anything in those factories. Some steps were performed in cleaner rooms (not clean rooms by todays standards)


They do use induction heating to heat all the metal during vacuuming the gas out, and then again later to flash the getter. so they were using them back in the 50's, that for sure.

Mullard - The Blackburn Vacuum Tubes Factory (Full) - YouTube
The Manufacture of Radio Valves - Presented by Mullard - YouTube
Wonderful English accent in these videos, easy to follow, Thanks for posting.
This Japanese 300B factory is a Hospital grade clean:
EMS???EMS?????????????????????????????

I was though these powerful induction heater could be the source from some damage in modern 300B tubes, but seems not true.
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Old 7th March 2013, 01:01 AM   #104
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Quote:
Originally Posted by Parafeed813 View Post
After reading the pdf I was a bit disappointed about the lack of scientific content. In the text the only reference to another publication is to a book of the author himself.
Furthermore, where are the statistics that there is actually a problem that needs solving?
If, over several decades some gas has found its way into the internals of a valve, that gas can only be air: 20% oxigen, 79% nitrogen and 1% argon. A barium getter will quickly react with the oxigen, but it does nothing with the other gasses. So, if the problem is gas coming from outside, even 'reactivating' the barium getter still leaves 80% of the problem. Big deal.

In his own collection of two types of small signal valves he found improvement after baking the problem valves. What would have happened to those if they would just have been used in a real circuit? Is cathode poisoning in these cases a likely danger? Give me numbers: what percentage of valves die because of this? How much shorter valve life? Differences between small signal, power and transmitting types?

I'm not saying that the problem the author describes is not real, because I do not know. All I know is that I just plug in old valves and most of them just work perfectly.
After reading the pdf I was a bit disappointed about the lack of scientific content.
Ditto here, mainly for this be a famous author, he just related his test on the kitchen.
I conclude baking tubes are suited only to full glass DHT tubes without baquelite base.
Senile big ham radio tubes also not benefit from baking, as they can be heated in the RF amp without the HV for days.

I suspect these usual dust barium getter used on the tube glass had more some chemical elements than just barium.

Is cathode poisoning in these cases a likely danger?
It is a danger to ruin the tube, it is a subject that needs much more study, Iam sure the tubes factories know alot about it.
They just dont say it to us.
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Old 7th March 2013, 03:03 AM   #105
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Quote:
Originally Posted by wicked1 View Post
after watching that, some Mullard Blackburn video's from the 50's or 60's showed up, and they were incredible!! They NEVER touched anything in those factories. Some steps were performed in cleaner rooms (not clean rooms by todays standards)


They do use induction heating to heat all the metal during vacuuming the gas out, and then again later to flash the getter. so they were using them back in the 50's, that for sure.
Very cool! Thanks for posting the Mullard videos, wicked1. They sure had lots of gloppata machines going back then!

I especially liked the draftsman working in suit and tie Very old-school, indeed!

The inductive-heating process is shown at about 22:45 in the "Manufacture" video (the shorter one). I suppose heating the internal elements red-hot during evacuation of the tube would also bake-off any impurities or finger-oils left on the parts during handling. They didn't seem to wash any of the parts after assembly and before insertion into the tubes - and the workers were certainly handling the innards with bare fingers, even in the Mullard factory back in the good-old-days...

And they most certainly were not working in anything resembling a clean-room! All those gloppata machines need oiling, the high factory ceilings with "winged-residents", the open windows back in the days when roads may or (more likely) may not have been paved.

A testament to the ruggedness of tubes, indeed!

Just try processing a wafer of silicon under THOSE conditions!!

Again - seriously - are we really concerned about somehow baking the getter in older tubes after watching some of these videos? Life is short, there's lots of amps to build and beaches to go explore.

Perspective, people, perspective.

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Old 7th March 2013, 10:32 AM   #106
DF96 is offline DF96  England
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Quote:
Originally Posted by Parafeed813
If, over several decades some gas has found its way into the internals of a valve, that gas can only be air: 20% oxigen, 79% nitrogen and 1% argon. A barium getter will quickly react with the oxigen, but it does nothing with the other gasses. So, if the problem is gas coming from outside, even 'reactivating' the barium getter still leaves 80% of the problem. Big deal.
As precisely the same problem appears to be solved by the getter during manufacture, I assume the getter can mop up nitrogen OK. Metals do form nitrides! Argon maybe not.

Quote:
Originally Posted by rfengineer2013
The inductive-heating process is shown at about 22:45 in the "Manufacture" video (the shorter one). I suppose heating the internal elements red-hot during evacuation of the tube would also bake-off any impurities or finger-oils left on the parts during handling. They didn't seem to wash any of the parts after assembly and before insertion into the tubes - and the workers were certainly handling the innards with bare fingers, even in the Mullard factory back in the good-old-days...
I suspect that touching most metal parts does not matter too much. Occasionally a partial fingerprint can be seen on an anode. The cathode surface is different; that should never be touched.
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Old 7th March 2013, 12:35 PM   #107
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"And they most certainly were not working in anything resembling a clean-room! All those gloppata machines need oiling, the high factory ceilings with "winged-residents", the open windows back in the days when roads may or (more likely) may not have been paved".

Unpaved roads in the UK in the 50's? What part of Fairyland are you from?

Last edited by radiosmuck; 7th March 2013 at 12:36 PM. Reason: inverted comma's added
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Old 7th March 2013, 12:43 PM   #108
wicked1 is offline wicked1  United States
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Other than the demonstrations, I thought they used tools all the time (rather than fingers), on the inner pieces.. Pliers, etc. Then they even mention the "new" production line is automatic "and you'll notice they are not touched by a human hand" or something the announcer says.
and the "clean room" I mention was at a couple of particular phases in the manufacture parts are assembeled behind glass in a separate room, away from the main assembly line.

But yeah, quite industrial!
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Old 7th March 2013, 02:41 PM   #109
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Quote:
Originally Posted by DF96 View Post
As precisely the same problem appears to be solved by the getter during manufacture, I assume the getter can mop up nitrogen OK. Metals do form nitrides! Argon maybe not.


I suspect that touching most metal parts does not matter too much. Occasionally a partial fingerprint can be seen on an anode. The cathode surface is different; that should never be touched.
Occasionally a partial fingerprint can be seen on an anode.
I bake two Ulianov 6C33, on the next day appear inside of the tube glass base(next to the pins) a very white partial fingerprint.
So in the 1983 Ulianov factory they dont used gloves.
I will post a complete report as the getter tubes are changing yet.
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Old 7th March 2013, 03:35 PM   #110
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Who wants to try this out?
Simple DIY Induction Heater - RMCybernetics
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