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Old 17th April 2003, 11:26 PM   #21
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Default Re: Paradox.

Quote:
Originally posted by fdegrove
Cathode poisoning is one of the reasons.

It may take a lenghty explanation of what exactly goes on here, maybe someone more clever than me can condense it in a few lines....?
I didn't know that cool cathodes could provoke cathode poisoning. Why?
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Old 17th April 2003, 11:48 PM   #22
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Exclamation POISON.

Hi,

Quote:
I didn't know that cool cathodes could provoke cathode poisoning. Why?
It does, as I said earlier it may take a lenghty translation exercise on my part but rest assured it's not healthy for the tubes.
Granted, the study is based on MTBF studies done on CRTs but it applies to any tube really.

The documents were publishished by the Dutch (defunct?) mag Audio & Techniek and covered AC versus DC heating etc.
The invitee was an ex Philips engineer, the redaction plus some audionuts such as Audio Note importer Ed de Jong, some other people I can't quite remember and yours truly.

This poisoning is one reason why I so often object on totally unnecessary stand-by arrangements such as leaving 1/2 B+ on the anodes or reducing heater voltages by half and so on.

One can actually create new types of tubes by "forming" them on particular voltages for a while, it seems tubes have some kind of memory as most other parts but I'm pushing...

If you like I can dig up that document and mail it to you, it's slightly over 1 Megabyte in size and in PDF format thanks to fellow member Remco (AKA Analogue something...).

Cheers,
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Old 17th April 2003, 11:59 PM   #23
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Default STANDING OVATION.

Hi,

Quote:
May I soundly applaud you on your desire to find about more about the valves you use!
Absolutely...wish we had more members like this.

Quite refreshing after a long series of the kind look Ma what I found in the junk box...anything I can do with it ?
How do I tack this odd-ball to that one, etc and manage to drive half the forum nuts with impossible questions.

Sorry to sound harsh,
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Old 18th April 2003, 12:02 AM   #24
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Default Re: POISON.

Quote:
Originally posted by fdegrove
If you like I can dig up that document and mail it to you, it's slightly over 1 Megabyte in size and in PDF format thanks to fellow member Remco (AKA Analogue something...).
Yes, please.

Just to add confusion, studio tube cameras always ran their tubes in standby to extend their life. (63% heater voltage, then full heater voltage, then HT after one minute delay.) Each of our four cameras used four tubes, and at 1,500 a pop, you really wanted to get every hour you could out of them. They typically lasted 3,000 hours, although we had a couple that were 17,000 hours old, and still producing nice pictures.
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Old 18th April 2003, 12:22 AM   #25
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Default NO CONFUSION HERE.

Hi,

Remind me to send this to you, ( I'm going to be busy for weeks to come) mind you it is in Dutch so you will have to run it through one of those magnificent translation engines.

After that you may be able to collect on a big bonus from your employer...

Ciao,
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Old 18th April 2003, 12:43 AM   #26
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Default POETRY

I look forward to seeing the results of passing a technical paper through a translation engine!
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Old 18th April 2003, 12:50 AM   #27
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Default LYRICS.

Hi,

Quote:
I look forward to seeing the results of passing a technical paper through a translation engine!
Don't despair...I'll help with my lousy English.
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Old 18th April 2003, 01:15 AM   #28
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Default The state of education

Sadly, your English is better than the majority of (UK) students. What do they teach the kids at school? Whinge, gripe, whine.
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Old 18th April 2003, 06:13 AM   #29
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Default Mr. Microwave speaks.....

In the world of microwave TWTs, heater voltage is very tightly controlled for maximum tube life and performance. Too high, and yep, it dies too fast. Too cold, the tube gets "gassy", and emission goes down.....which leads to high helix current, and......etc....

In brief, it kills tubes also. I would assume that much the same applies to conventional small signal tubes. Although I suspect lower heater voltage.......within reason......... would not have as great a negative effect.

Jocko
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Old 18th April 2003, 06:42 AM   #30
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Cool Tube Life

Hi,
My uncle was most of his professional life into tubes.
He found that halving the cathode-anode voltage at least doubled the life time of the tube.
Elso /not into tubes.
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